Patchwork [RFC,v2,3/3] block: add sheepdog driver for distributed storage support

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Submitter MORITA Kazutaka
Date May 14, 2010, 9:51 a.m.
Message ID <1273830676-2349-4-git-send-email-morita.kazutaka@lab.ntt.co.jp>
Download mbox | patch
Permalink /patch/52601/
State New
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Comments

MORITA Kazutaka - May 14, 2010, 9:51 a.m.
Sheepdog is a distributed storage system for QEMU. It provides highly
available block level storage volumes to VMs like Amazon EBS.  This
patch adds a qemu block driver for Sheepdog.

Sheepdog features are:
- No node in the cluster is special (no metadata node, no control
  node, etc)
- Linear scalability in performance and capacity
- No single point of failure
- Autonomous management (zero configuration)
- Useful volume management support such as snapshot and cloning
- Thin provisioning
- Autonomous load balancing

The more details are available at the project site:
    http://www.osrg.net/sheepdog/

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
---
 Makefile.objs    |    2 +-
 block/sheepdog.c | 1831 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 1832 insertions(+), 1 deletions(-)
 create mode 100644 block/sheepdog.c
Kevin Wolf - May 14, 2010, 11:08 a.m.
Am 14.05.2010 11:51, schrieb MORITA Kazutaka:
> Sheepdog is a distributed storage system for QEMU. It provides highly
> available block level storage volumes to VMs like Amazon EBS.  This
> patch adds a qemu block driver for Sheepdog.
> 
> Sheepdog features are:
> - No node in the cluster is special (no metadata node, no control
>   node, etc)
> - Linear scalability in performance and capacity
> - No single point of failure
> - Autonomous management (zero configuration)
> - Useful volume management support such as snapshot and cloning
> - Thin provisioning
> - Autonomous load balancing
> 
> The more details are available at the project site:
>     http://www.osrg.net/sheepdog/
> 
> Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>

Once we solved the image creation thing, I think I'm going to be happy
with the block interface. Of course, this is something that doesn't even
directly affect the driver code, just the way it is used.

I have no clue about the Sheepdog protocol, so I'm just trying to
comment on some general details.

> ---
>  Makefile.objs    |    2 +-
>  block/sheepdog.c | 1831 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 1832 insertions(+), 1 deletions(-)
>  create mode 100644 block/sheepdog.c
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index ecdd53e..6edbc57 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -14,7 +14,7 @@ block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>  
>  block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat.o
>  block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
> -block-nested-y += parallels.o nbd.o blkdebug.o
> +block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o
>  block-nested-$(CONFIG_WIN32) += raw-win32.o
>  block-nested-$(CONFIG_POSIX) += raw-posix.o
>  block-nested-$(CONFIG_CURL) += curl.o
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> new file mode 100644
> index 0000000..adf3a71
> --- /dev/null
> +++ b/block/sheepdog.c
> @@ -0,0 +1,1831 @@
> +/*
> + * Copyright (C) 2009-2010 Nippon Telegraph and Telephone Corporation.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License version
> + * 2 as published by the Free Software Foundation.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +#include <netdb.h>
> +#include <netinet/tcp.h>
> +
> +#include "qemu-common.h"
> +#include "block_int.h"
> +
> +#define SD_PROTO_VER 0x01
> +
> +#define SD_DEFAULT_ADDR "localhost:7000"
> +
> +#define SD_OP_CREATE_AND_WRITE_OBJ  0x01
> +#define SD_OP_READ_OBJ       0x02
> +#define SD_OP_WRITE_OBJ      0x03
> +
> +#define SD_OP_NEW_VDI        0x11
> +#define SD_OP_LOCK_VDI       0x12
> +#define SD_OP_RELEASE_VDI    0x13
> +#define SD_OP_GET_VDI_INFO   0x14
> +#define SD_OP_READ_VDIS      0x15
> +
> +#define SD_FLAG_CMD_WRITE    0x01
> +#define SD_FLAG_CMD_COW      0x02
> +
> +#define SD_RES_SUCCESS       0x00 /* Success */
> +#define SD_RES_UNKNOWN       0x01 /* Unknown error */
> +#define SD_RES_NO_OBJ        0x02 /* No object found */
> +#define SD_RES_EIO           0x03 /* I/O error */
> +#define SD_RES_VDI_EXIST     0x04 /* Vdi exists already */
> +#define SD_RES_INVALID_PARMS 0x05 /* Invalid parameters */
> +#define SD_RES_SYSTEM_ERROR  0x06 /* System error */
> +#define SD_RES_VDI_LOCKED    0x07 /* Vdi is locked */
> +#define SD_RES_NO_VDI        0x08 /* No vdi found */
> +#define SD_RES_NO_BASE_VDI   0x09 /* No base vdi found */
> +#define SD_RES_VDI_READ      0x0A /* Cannot read requested vdi */
> +#define SD_RES_VDI_WRITE     0x0B /* Cannot write requested vdi */
> +#define SD_RES_BASE_VDI_READ 0x0C /* Cannot read base vdi */
> +#define SD_RES_BASE_VDI_WRITE   0x0D /* Cannot write base vdi */
> +#define SD_RES_NO_TAG        0x0E /* Requested tag is not found */
> +#define SD_RES_STARTUP       0x0F /* Sheepdog is on starting up */
> +#define SD_RES_VDI_NOT_LOCKED   0x10 /* Vdi is not locked */
> +#define SD_RES_SHUTDOWN      0x11 /* Sheepdog is shutting down */
> +#define SD_RES_NO_MEM        0x12 /* Cannot allocate memory */
> +#define SD_RES_FULL_VDI      0x13 /* we already have the maximum vdis */
> +#define SD_RES_VER_MISMATCH  0x14 /* Protocol version mismatch */
> +#define SD_RES_NO_SPACE      0x15 /* Server has no room for new objects */
> +#define SD_RES_WAIT_FOR_FORMAT  0x16 /* Sheepdog is waiting for a format operation */
> +#define SD_RES_WAIT_FOR_JOIN    0x17 /* Sheepdog is waiting for other nodes joining */
> +#define SD_RES_JOIN_FAILED   0x18 /* Target node had failed to join sheepdog */
> +
> +/*
> + * Object ID rules
> + *
> + *  0 - 19 (20 bits): data object space
> + * 20 - 31 (12 bits): reserved data object space
> + * 32 - 55 (24 bits): vdi object space
> + * 56 - 59 ( 4 bits): reserved vdi object space
> + * 60 - 63 ( 4 bits): object type indentifier space
> + */
> +
> +#define VDI_SPACE_SHIFT   32
> +#define VDI_BIT (UINT64_C(1) << 63)
> +#define VMSTATE_BIT (UINT64_C(1) << 62)
> +#define MAX_DATA_OBJS (1ULL << 20)
> +#define MAX_CHILDREN 1024
> +#define SD_MAX_VDI_LEN 256
> +#define SD_NR_VDIS   (1U << 24)
> +#define SD_DATA_OBJ_SIZE (UINT64_C(1) << 22)
> +
> +#define SD_INODE_SIZE (sizeof(struct sd_inode))
> +#define CURRENT_VDI_ID 0
> +
> +struct sd_req {
> +	uint8_t		proto_ver;
> +	uint8_t		opcode;
> +	uint16_t	flags;
> +	uint32_t	epoch;
> +	uint32_t        id;
> +	uint32_t        data_length;
> +	uint32_t	opcode_specific[8];
> +};

CODING_STYLE says that structs should be typedefed and their names
should be in CamelCase. So something like this:

typedef struct SheepdogReq {
    ...
} SheepdogReq;

(Or, if your prefer, SDReq; but with things like SDAIOCB I think it
becomes hard to read)

> +
> +struct sd_rsp {
> +	uint8_t		proto_ver;
> +	uint8_t		opcode;
> +	uint16_t	flags;
> +	uint32_t	epoch;
> +	uint32_t        id;
> +	uint32_t        data_length;
> +	uint32_t        result;
> +	uint32_t	opcode_specific[7];
> +};
> +
> +struct sd_obj_req {
> +	uint8_t		proto_ver;
> +	uint8_t		opcode;
> +	uint16_t	flags;
> +	uint32_t	epoch;
> +	uint32_t        id;
> +	uint32_t        data_length;
> +	uint64_t        oid;
> +	uint64_t        cow_oid;
> +	uint32_t        copies;
> +	uint32_t        rsvd;
> +	uint64_t        offset;
> +};
> +
> +struct sd_obj_rsp {
> +	uint8_t		proto_ver;
> +	uint8_t		opcode;
> +	uint16_t	flags;
> +	uint32_t	epoch;
> +	uint32_t        id;
> +	uint32_t        data_length;
> +	uint32_t        result;
> +	uint32_t        copies;
> +	uint32_t        pad[6];
> +};
> +
> +struct sd_vdi_req {
> +	uint8_t		proto_ver;
> +	uint8_t		opcode;
> +	uint16_t	flags;
> +	uint32_t	epoch;
> +	uint32_t        id;
> +	uint32_t        data_length;
> +	uint64_t	vdi_size;
> +	uint32_t        base_vdi_id;
> +	uint32_t        copies;
> +	uint32_t        snapid;
> +	uint32_t        pad[3];
> +};
> +
> +struct sd_vdi_rsp {
> +	uint8_t		proto_ver;
> +	uint8_t		opcode;
> +	uint16_t	flags;
> +	uint32_t	epoch;
> +	uint32_t        id;
> +	uint32_t        data_length;
> +	uint32_t        result;
> +	uint32_t        rsvd;
> +	uint32_t        vdi_id;
> +	uint32_t        pad[5];
> +};
> +
> +struct sd_inode {
> +	char name[SD_MAX_VDI_LEN];
> +	uint64_t ctime;
> +	uint64_t snap_ctime;
> +	uint64_t vm_clock_nsec;
> +	uint64_t vdi_size;
> +	uint64_t vm_state_size;
> +	uint16_t copy_policy;
> +	uint8_t  nr_copies;
> +	uint8_t  block_size_shift;
> +	uint32_t snap_id;
> +	uint32_t vdi_id;
> +	uint32_t parent_vdi_id;
> +	uint32_t child_vdi_id[MAX_CHILDREN];
> +	uint32_t data_vdi_id[MAX_DATA_OBJS];
> +};
> +
> +/*
> + * 64 bit FNV-1a non-zero initial basis
> + */
> +#define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
> +
> +/*
> + * 64 bit Fowler/Noll/Vo FNV-1a hash code
> + */
> +static inline uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval)
> +{
> +        unsigned char *bp = (unsigned char *) buf;
> +        unsigned char *be = bp + len;
> +        while (bp < be) {
> +                hval ^= (uint64_t) *bp++;
> +                hval += (hval << 1) + (hval << 4) + (hval << 5) +
> +                        (hval << 7) + (hval << 8) + (hval << 40);
> +        }
> +        return hval;
> +}
> +
> +static inline int is_data_obj_writeable(struct sd_inode *inode, unsigned int idx)
> +{
> +	return inode->vdi_id == inode->data_vdi_id[idx];
> +}
> +
> +static inline int is_data_obj(uint64_t oid)
> +{
> +	return !(VDI_BIT & oid);
> +}
> +
> +static inline uint64_t data_oid_to_idx(uint64_t oid)
> +{
> +	return oid & (MAX_DATA_OBJS - 1);
> +}
> +
> +static inline uint64_t vid_to_vdi_oid(uint32_t vid)
> +{
> +	return VDI_BIT | ((uint64_t)vid << VDI_SPACE_SHIFT);
> +}
> +
> +static inline uint64_t vid_to_vmstate_oid(uint32_t vid, uint32_t idx)
> +{
> +	return VMSTATE_BIT | ((uint64_t)vid << VDI_SPACE_SHIFT) | idx;
> +}
> +
> +static inline uint64_t vid_to_data_oid(uint32_t vid, uint32_t idx)
> +{
> +	return ((uint64_t)vid << VDI_SPACE_SHIFT) | idx;
> +}
> +
> +#undef eprintf
> +#define eprintf(fmt, args...)						\
> +do {									\
> +	fprintf(stderr, "%s %d: " fmt, __func__, __LINE__, ##args);	\
> +} while (0)

What about using error_report() instead of fprintf? Though it should be
the same currently.

> +
> +#undef dprintf
> +#ifdef DEBUG_SDOG
> +#define dprintf(fmt, args...)						\
> +do {									\
> +	fprintf(stdout, "%s %d: " fmt, __func__, __LINE__, ##args);	\
> +} while (0)
> +#else
> +#define dprintf(fmt, args...)
> +#endif
> +
> +#define min_t(type, x, y) ({			\
> +	type __min1 = (x);			\
> +	type __min2 = (y);			\
> +	__min1 < __min2 ? __min1: __min2; })
> +
> +struct aio_req {
> +	struct sd_aiocb *aiocb;
> +	unsigned int iov_offset;
> +
> +	uint64_t oid;
> +	uint64_t base_oid;
> +	uint64_t offset;
> +	unsigned int data_len;
> +	uint8_t flags;
> +
> +	QLIST_ENTRY(aio_req) pending_siblings;
> +	QLIST_ENTRY(aio_req) aioreq_siblings;
> +};
> +
> +enum aiocb_state {
> +	AIOCB_WRITE_UDATA,
> +	AIOCB_READ_UDATA,
> +};
> +
> +struct sd_aiocb {
> +	BlockDriverAIOCB common;
> +
> +	QEMUIOVector *qiov;
> +
> +	int64_t sector_num;
> +	int nb_sectors;
> +
> +	int ret;
> +	enum aiocb_state aiocb_type;
> +
> +	QEMUBH *bh;
> +	void (*aio_done_func)(struct sd_aiocb *);
> +
> +	int canceled;
> +
> +	QLIST_HEAD(aioreq_head, aio_req) aioreq_head;
> +};
> +
> +#define MAX_AIO_REQS 4096
> +
> +struct bdrv_sd_state {
> +	struct sd_inode inode;
> +
> +	int nr_dirty_data_oids;
> +	uint32_t dirty_data_oids[MAX_AIO_REQS];
> +
> +	char name[SD_MAX_VDI_LEN];
> +	int is_current;
> +
> +	char *addr;
> +	int fd;
> +
> +	struct aio_req aio_req_list[MAX_AIO_REQS];
> +	struct aio_req *aio_req_free[MAX_AIO_REQS];
> +	int nr_aio_req_free;
> +
> +	QLIST_HEAD(pending_head, aio_req) pending_head;
> +};
> +
> +static const char * sd_strerror(int err)
> +{
> +	int i;
> +
> +	static const struct {
> +		int err;
> +		const char *desc;
> +	} errors[] = {
> +		{SD_RES_SUCCESS, "Success"},
> +		{SD_RES_UNKNOWN, "Unknown error"},
> +		{SD_RES_NO_OBJ, "No object found"},
> +		{SD_RES_EIO, "I/O error"},
> +		{SD_RES_VDI_EXIST, "VDI exists already"},
> +		{SD_RES_INVALID_PARMS, "Invalid parameters"},
> +		{SD_RES_SYSTEM_ERROR, "System error"},
> +		{SD_RES_VDI_LOCKED, "VDI is already locked"},
> +		{SD_RES_NO_VDI, "No vdi found"},
> +		{SD_RES_NO_BASE_VDI, "No base VDI found"},
> +		{SD_RES_VDI_READ, "Failed read the requested VDI"},
> +		{SD_RES_VDI_WRITE, "Failed to write the requested VDI"},
> +		{SD_RES_BASE_VDI_READ, "Failed to read the base VDI"},
> +		{SD_RES_BASE_VDI_WRITE, "Failed to write the base VDI"},
> +		{SD_RES_NO_TAG, "Failed to find the requested tag"},
> +		{SD_RES_STARTUP, "The system is still booting"},
> +		{SD_RES_VDI_NOT_LOCKED, "VDI isn't locked"},
> +		{SD_RES_SHUTDOWN, "The system is shutting down"},
> +		{SD_RES_NO_MEM, "Out of memory on the server"},
> +		{SD_RES_FULL_VDI, "We already have the maximum vdis"},
> +		{SD_RES_VER_MISMATCH, "Protocol version mismatch"},
> +		{SD_RES_NO_SPACE, "Server has no space for new objects"},
> +		{SD_RES_WAIT_FOR_FORMAT, "Sheepdog is waiting for a format operation"},
> +		{SD_RES_WAIT_FOR_JOIN, "Sheepdog is waiting for other nodes joining"},
> +		{SD_RES_JOIN_FAILED, "Target node had failed to join sheepdog"},
> +	};
> +
> +	for (i = 0; i < ARRAY_SIZE(errors); ++i)
> +		if (errors[i].err == err)
> +			return errors[i].desc;

CODING_STYLE requires braces here.

> +
> +	return "Invalid error code";
> +}
> +
> +static inline int before(uint32_t seq1, uint32_t seq2)
> +{
> +        return (int32_t)(seq1 - seq2) < 0;
> +}
> +
> +static inline int after(uint32_t seq1, uint32_t seq2)
> +{
> +	return (int32_t)(seq2 - seq1) < 0;
> +}

These functions look strange... Is the difference to seq1 < seq2 that
the cast introduces intentional? (after(0x0, 0xabcdefff) == 1)

If yes, why is this useful? This needs a comment. If no, why even bother
to have this function instead of directly using < or > ?

> +
> +static inline struct aio_req *alloc_aio_req(struct bdrv_sd_state *s,
> +					    struct sd_aiocb *acb,
> +					    uint64_t oid, unsigned int data_len,
> +					    uint64_t offset, uint8_t flags,
> +					    uint64_t base_oid,
> +					    unsigned int iov_offset)
> +{
> +	struct aio_req *aio_req;
> +
> +	if (!s->nr_aio_req_free)
> +		return NULL;
> +
> +	aio_req = s->aio_req_free[--s->nr_aio_req_free];
> +	aio_req->aiocb = acb;
> +	aio_req->iov_offset = iov_offset;
> +	aio_req->oid = oid;
> +	aio_req->base_oid = base_oid;
> +	aio_req->offset = offset;
> +	aio_req->data_len = data_len;
> +	aio_req->flags = flags;
> +
> +	QLIST_INSERT_HEAD(&s->pending_head, aio_req, pending_siblings);
> +	QLIST_INSERT_HEAD(&acb->aioreq_head, aio_req, aioreq_siblings);
> +
> +	return aio_req;
> +}
> +
> +static inline int free_aio_req(struct bdrv_sd_state *s, struct aio_req *aio_req)
> +{
> +	struct sd_aiocb *acb = aio_req->aiocb;
> +	QLIST_REMOVE(aio_req, pending_siblings);
> +	QLIST_REMOVE(aio_req, aioreq_siblings);
> +	aio_req->aiocb = NULL;
> +	s->aio_req_free[s->nr_aio_req_free++] = aio_req;
> +
> +	return !QLIST_EMPTY(&acb->aioreq_head);
> +}
> +
> +static inline int nr_outstanding_aio_req(struct bdrv_sd_state *s)
> +{
> +	return MAX_AIO_REQS - s->nr_aio_req_free;
> +}
> +
> +static inline int get_id_from_req(struct bdrv_sd_state *s, struct aio_req *aio_req)
> +{
> +	return aio_req - s->aio_req_list;
> +}
> +
> +static inline struct aio_req *get_req_from_id(struct bdrv_sd_state *s, int id)
> +{
> +	return s->aio_req_list + id;
> +}
> +
> +static void sd_finish_aiocb(struct sd_aiocb *acb)
> +{
> +	if (!acb->canceled)
> +		acb->common.cb(acb->common.opaque, acb->ret);
> +	qemu_aio_release(acb);
> +}
> +
> +static void sd_aio_cancel(BlockDriverAIOCB *blockacb)
> +{
> +	struct sd_aiocb *acb = (struct sd_aiocb *)blockacb;
> +
> +	acb->canceled = 1;
> +}
> +
> +static AIOPool sd_aio_pool = {
> +	.aiocb_size = sizeof(struct sd_aiocb),
> +	.cancel = sd_aio_cancel,
> +};
> +
> +static struct sd_aiocb *sd_aio_setup(BlockDriverState *bs, QEMUIOVector *qiov,
> +				     int64_t sector_num, int nb_sectors,
> +				     BlockDriverCompletionFunc *cb,
> +				     void *opaque)
> +{
> +	struct sd_aiocb *acb;
> +
> +	acb = qemu_aio_get(&sd_aio_pool, bs, cb, opaque);
> +
> +	acb->qiov = qiov;
> +
> +	acb->sector_num = sector_num;
> +	acb->nb_sectors = nb_sectors;
> +
> +	acb->aio_done_func = NULL;
> +	acb->canceled = 0;
> +	acb->bh = NULL;
> +	acb->ret = 0;
> +	QLIST_INIT(&acb->aioreq_head);
> +	return acb;
> +}
> +
> +static int sd_schedule_bh(QEMUBHFunc *cb, struct sd_aiocb *acb)
> +{
> +	if (acb->bh) {
> +		eprintf("bug: %d %d\n", acb->aiocb_type, acb->aiocb_type);
> +		return -EIO;
> +	}
> +
> +	acb->bh = qemu_bh_new(cb, acb);
> +	if (!acb->bh) {
> +		eprintf("oom: %d %d\n", acb->aiocb_type, acb->aiocb_type);
> +		return -EIO;
> +	}
> +
> +	qemu_bh_schedule(acb->bh);
> +
> +	return 0;
> +}
> +
> +static int do_send_recv(int sockfd, struct iovec *iov, int len, int offset,
> +			int write)
> +{
> +	struct msghdr msg;
> +	int ret, diff;
> +
> +	memset(&msg, 0, sizeof(msg));
> +	msg.msg_iov = iov;
> +	msg.msg_iovlen = 1;
> +
> +	len += offset;
> +
> +	while (iov->iov_len < len) {
> +		len -= iov->iov_len;
> +
> +		iov++;
> +		msg.msg_iovlen++;
> +	}
> +
> +	diff = iov->iov_len - len;
> +	iov->iov_len -= diff;
> +
> +	while (msg.msg_iov->iov_len <= offset) {
> +		offset -= msg.msg_iov->iov_len;
> +
> +		msg.msg_iov++;
> +		msg.msg_iovlen--;
> +	}
> +
> +	msg.msg_iov->iov_base = (char *) msg.msg_iov->iov_base + offset;
> +	msg.msg_iov->iov_len -= offset;
> +
> +	if (write)
> +		ret = sendmsg(sockfd, &msg, 0);
> +	else
> +		ret = recvmsg(sockfd, &msg, MSG_WAITALL);
> +
> +	msg.msg_iov->iov_base = (char *) msg.msg_iov->iov_base - offset;
> +	msg.msg_iov->iov_len += offset;
> +
> +	iov->iov_len += diff;
> +	return ret;
> +}
> +
> +static int connect_to_sdog(const char *addr)
> +{
> +	char buf[64];
> +	char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
> +	char name[256], *p;
> +	int fd, ret;
> +	struct addrinfo hints, *res, *res0;
> +	int port = 0;
> +
> +	if (!addr)
> +		addr = SD_DEFAULT_ADDR;
> +
> +	strcpy(name, addr);
> +
> +	p = name;
> +	while (*p) {
> +		if (*p == ':') {
> +			*p++ = '\0';
> +			break;
> +		} else
> +			p++;
> +	}
> +
> +	if (*p == '\0') {
> +		eprintf("cannot find a port number, %s\n", name);
> +		return -1;
> +	}
> +	port = strtol(p, NULL, 10);
> +	if (port == 0) {
> +		eprintf("invalid port number, %s\n", p);
> +		return -1;
> +	}
> +
> +	memset(&hints, 0, sizeof(hints));
> +	snprintf(buf, sizeof(buf), "%d", port);
> +
> +	hints.ai_socktype = SOCK_STREAM;
> +
> +	ret = getaddrinfo(name, buf, &hints, &res0);
> +	if (ret) {
> +		eprintf("unable to get address info %s, %m\n", name);
> +		return -1;
> +	}
> +
> +	for (res = res0; res; res = res->ai_next) {
> +		ret = getnameinfo(res->ai_addr, res->ai_addrlen,
> +				  hbuf, sizeof(hbuf), sbuf, sizeof(sbuf),
> +				  NI_NUMERICHOST | NI_NUMERICSERV);
> +		if (ret)
> +			continue;
> +
> +		fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
> +		if (fd < 0)
> +			continue;
> +
> +reconnect:
> +		ret = connect(fd, res->ai_addr, res->ai_addrlen);
> +		if (ret < 0) {
> +			if (errno == EINTR)
> +				goto reconnect;
> +			break;
> +		}
> +
> +		dprintf("connected to %s:%d\n", name, port);
> +		goto success;
> +	}
> +	fd = -1;
> +	eprintf("failed connect to %s:%d\n", name, port);
> +success:
> +	freeaddrinfo(res0);
> +	return fd;
> +}
> +
> +static int do_readv_writev(int sockfd, struct iovec *iov, int len,
> +			   int iov_offset, int write)
> +{
> +	int ret;
> +again:
> +	ret = do_send_recv(sockfd, iov, len, iov_offset, write);
> +	if (ret < 0) {
> +		if (errno == EINTR || errno == EAGAIN)
> +			goto again;
> +		eprintf("failed to recv a rsp, %m\n");
> +		return 1;
> +	}
> +
> +	iov_offset += ret;
> +	len -= ret;
> +	if (len)
> +		goto again;
> +
> +	return 0;
> +}
> +
> +static int do_readv(int sockfd, struct iovec *iov, int len, int iov_offset)
> +{
> +	return do_readv_writev(sockfd, iov, len, iov_offset, 0);
> +}
> +
> +static int do_writev(int sockfd, struct iovec *iov, int len, int iov_offset)
> +{
> +	return do_readv_writev(sockfd, iov, len, iov_offset, 1);
> +}
> +
> +static int do_read_write(int sockfd, void *buf, int len, int write)
> +{
> +	struct iovec iov;
> +
> +	iov.iov_base = buf;
> +	iov.iov_len = len;
> +
> +	return do_readv_writev(sockfd, &iov, len, 0, write);
> +}
> +
> +static int do_read(int sockfd, void *buf, int len)
> +{
> +	return do_read_write(sockfd, buf, len, 0);
> +}
> +
> +static int do_write(int sockfd, void *buf, int len)
> +{
> +	return do_read_write(sockfd, buf, len, 1);
> +}
> +
> +static int send_req(int sockfd, struct sd_req *hdr, void *data,
> +		    unsigned int *wlen)
> +{
> +	int ret;
> +	struct iovec iov[2];
> +
> +	iov[0].iov_base = hdr;
> +	iov[0].iov_len = sizeof(*hdr);
> +
> +	if (*wlen) {
> +		iov[1].iov_base = data;
> +		iov[1].iov_len = *wlen;
> +	}
> +
> +	ret = do_writev(sockfd, iov, sizeof(*hdr) + *wlen, 0);
> +	if (ret) {
> +		eprintf("failed to send a req, %m\n");
> +		ret = -1;
> +	}
> +
> +	return ret;
> +}
> +
> +static int do_req(int sockfd, struct sd_req *hdr, void *data,
> +		  unsigned int *wlen, unsigned int *rlen)
> +{
> +	int ret;
> +
> +	ret = send_req(sockfd, hdr, data, wlen);
> +	if (ret) {
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	ret = do_read(sockfd, hdr, sizeof(*hdr));
> +	if (ret) {
> +		eprintf("failed to get a rsp, %m\n");
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	if (*rlen > hdr->data_length)
> +		*rlen = hdr->data_length;
> +
> +	if (*rlen) {
> +		ret = do_read(sockfd, data, *rlen);
> +		if (ret) {
> +			eprintf("failed to get the data, %m\n");
> +			ret = -1;
> +			goto out;
> +		}
> +	}
> +	ret = 0;
> +out:
> +	return ret;
> +}
> +
> +static int add_aio_request(struct bdrv_sd_state *s, struct aio_req *aio_req,
> +			   struct iovec *iov, int niov, int create,
> +			   enum aiocb_state aiocb_type);
> +
> +static void send_pending_req(struct bdrv_sd_state *s, uint64_t oid, uint32_t id)
> +{
> +	struct aio_req *aio_req, *next;
> +	struct sd_aiocb *acb;
> +	int ret;
> +
> +	QLIST_FOREACH_SAFE(aio_req, &s->pending_head, pending_siblings, next) {
> +		if (id == get_id_from_req(s, aio_req))
> +			continue;
> +		if (aio_req->oid != oid)
> +			continue;
> +
> +		acb = aio_req->aiocb;
> +		ret = add_aio_request(s, aio_req, acb->qiov->iov,
> +				      acb->qiov->niov, 0, acb->aiocb_type);
> +		if (ret < 0) {
> +			eprintf("add_aio_request is faled\n");
> +			free_aio_req(s, aio_req);
> +			if (QLIST_EMPTY(&acb->aioreq_head))
> +				sd_finish_aiocb(acb);
> +		}
> +	}
> +}
> +
> +static void aio_read_response(void *opaque)
> +{
> +	struct sd_obj_req hdr;
> +	struct sd_obj_rsp *rsp = (struct sd_obj_rsp *)&hdr;
> +	struct bdrv_sd_state *s = (struct bdrv_sd_state *)opaque;
> +	int fd = s->fd;
> +	int ret;
> +	struct aio_req *aio_req;
> +	struct sd_aiocb *acb;
> +	int rest;
> +	unsigned long idx;
> +
> +	if (!nr_outstanding_aio_req(s))
> +		return;
> +
> +	ret = do_read(fd, (void *)rsp, sizeof(*rsp));
> +	if (ret) {
> +		eprintf("failed to get the header, %m\n");
> +		return;
> +	}
> +
> +	aio_req = get_req_from_id(s, rsp->id);
> +	acb = aio_req->aiocb;
> +
> +	switch (acb->aiocb_type) {
> +	case AIOCB_WRITE_UDATA:
> +		if (!is_data_obj(aio_req->oid))
> +			break;
> +		idx = data_oid_to_idx(aio_req->oid);
> +
> +		if (s->inode.data_vdi_id[idx] != s->inode.vdi_id) {
> +			s->inode.data_vdi_id[idx] = s->inode.vdi_id;
> +			s->dirty_data_oids[s->nr_dirty_data_oids++] = idx;
> +
> +			send_pending_req(s, vid_to_data_oid(s->inode.vdi_id, idx),
> +					 rsp->id);
> +		}
> +		break;
> +	case AIOCB_READ_UDATA:
> +		ret = do_readv(fd, acb->qiov->iov, rsp->data_length,
> +			       aio_req->iov_offset);
> +		if (ret) {
> +			eprintf("failed to get the data, %m\n");
> +			return;
> +		}
> +		break;
> +	}
> +
> +	if (rsp->result != SD_RES_SUCCESS) {
> +		acb->ret = -EIO;
> +		eprintf("%s\n", sd_strerror(rsp->result));
> +	}
> +
> +	rest = free_aio_req(s, aio_req);
> +	if (!rest)
> +		acb->aio_done_func(acb);
> +}
> +
> +static int aio_flush_request(void *opaque)
> +{
> +	return nr_outstanding_aio_req((struct bdrv_sd_state *)opaque);
> +}
> +
> +static int set_nonblocking(int fd)
> +{
> +	int ret;
> +
> +	ret = fcntl(fd, F_GETFL);
> +	if (ret < 0) {
> +		eprintf("can't fcntl (F_GETFL), %m\n");
> +		close(fd);
> +	} else {
> +		ret = fcntl(fd, F_SETFL, ret | O_NONBLOCK);
> +		if (ret < 0)
> +			eprintf("can't fcntl (O_NONBLOCK), %m\n");
> +	}
> +
> +	return ret;
> +}
> +
> +static int set_nodelay(int fd)
> +{
> +	int ret, opt;
> +
> +	opt = 1;
> +	ret = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
> +	return ret;
> +}
> +
> +static int get_sheep_fd(struct bdrv_sd_state *s)
> +{
> +	int ret, fd;
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0) {
> +		eprintf("%m\n");
> +		return -1;
> +	}
> +
> +	ret = set_nonblocking(fd);
> +	if (ret) {
> +		eprintf("%m\n");
> +		close(fd);
> +		return -1;
> +	}
> +
> +	ret = set_nodelay(fd);
> +	if (ret) {
> +		eprintf("%m\n");
> +		close(fd);
> +		return -1;
> +	}
> +
> +	qemu_aio_set_fd_handler(fd, aio_read_response, NULL, aio_flush_request,
> +				NULL, s);
> +	s->fd = fd;
> +
> +	return fd;
> +}
> +
> +static int parse_vdiname(struct bdrv_sd_state *s, const char *filename,
> +			 char *vdi, int vdi_len, uint32_t *snapid)
> +{
> +	char *p, *q;
> +	int nr_sep;
> +
> +	p = q = strdup(filename);
> +
> +	if (!p)
> +		return 1;
> +
> +	nr_sep = 0;
> +	while (*p) {
> +		if (*p == ':')
> +			nr_sep++;
> +		if (nr_sep == 2)
> +			break;
> +		p++;
> +	}
> +
> +	if (nr_sep == 2)
> +		*p++ = '\0';
> +	else
> +		p = q;
> +
> +	strncpy(vdi, p, vdi_len);
> +
> +	p = strchr(vdi, ':');
> +	if (p) {
> +		*p++ = '\0';
> +		*snapid = strtol(p, NULL, 10);
> +	} else
> +		*snapid = CURRENT_VDI_ID; /* search current vdi */
> +
> +	if (nr_sep == 2)
> +		s->addr = q;
> +	else {
> +		free(q);
> +		s->addr = NULL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int find_vdi_name(struct bdrv_sd_state *s, char *filename, uint32_t snapid,
> +			 uint32_t *vid, int for_snapshot)
> +{
> +	int ret, fd;
> +	struct sd_vdi_req hdr;
> +	struct sd_vdi_rsp *rsp = (struct sd_vdi_rsp *)&hdr;
> +	unsigned int wlen, rlen = 0;
> +	char buf[SD_MAX_VDI_LEN];
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0)
> +		return -1;
> +
> +	memset(&hdr, 0, sizeof(hdr));
> +	snprintf(buf, sizeof(buf), "%s", filename);
> +	if (for_snapshot)
> +		hdr.opcode = SD_OP_GET_VDI_INFO;
> +	else
> +		hdr.opcode = SD_OP_LOCK_VDI;
> +	wlen = SD_MAX_VDI_LEN;
> +	hdr.proto_ver = SD_PROTO_VER;
> +	hdr.data_length = SD_MAX_VDI_LEN;
> +	hdr.snapid = snapid;
> +	hdr.flags = SD_FLAG_CMD_WRITE;
> +
> +	ret = do_req(fd, (struct sd_req *)&hdr, buf, &wlen, &rlen);
> +	if (ret) {
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	if (rsp->result != SD_RES_SUCCESS) {
> +		eprintf("%s, %s\n", sd_strerror(rsp->result), filename);
> +		ret = -1;
> +		goto out;
> +	}
> +	*vid = rsp->vdi_id;
> +
> +	ret = 0;
> +out:
> +	close(fd);
> +	return ret;
> +}
> +
> +static int add_aio_request(struct bdrv_sd_state *s, struct aio_req *aio_req,
> +			   struct iovec *iov, int niov, int create,
> +			   enum aiocb_state aiocb_type)
> +{
> +	int nr_copies = s->inode.nr_copies;
> +	struct sd_obj_req hdr;
> +	unsigned int wlen;
> +	int ret, opt;
> +	uint64_t oid = aio_req->oid;
> +	unsigned int datalen = aio_req->data_len;
> +	uint64_t offset = aio_req->offset;
> +	uint8_t flags = aio_req->flags;
> +	uint64_t old_oid = aio_req->base_oid;
> +
> +	if (!nr_copies)
> +		eprintf("bug\n");
> +
> +	memset(&hdr, 0, sizeof(hdr));
> +
> +	if (aiocb_type == AIOCB_READ_UDATA) {
> +		wlen = 0;
> +		hdr.opcode = SD_OP_READ_OBJ;
> +		hdr.flags = flags;
> +	} else if (create) {
> +		wlen = datalen;
> +		hdr.opcode = SD_OP_CREATE_AND_WRITE_OBJ;
> +		hdr.flags = SD_FLAG_CMD_WRITE | flags;
> +	} else {
> +		wlen = datalen;
> +		hdr.opcode = SD_OP_WRITE_OBJ;
> +		hdr.flags = SD_FLAG_CMD_WRITE | flags;
> +	}
> +
> +	hdr.oid = oid;
> +	hdr.cow_oid = old_oid;
> +	hdr.copies = s->inode.nr_copies;
> +
> +	hdr.data_length = datalen;
> +	hdr.offset = offset;
> +
> +	hdr.id = get_id_from_req(s, aio_req);
> +
> +	opt = 1;
> +	setsockopt(s->fd, SOL_TCP, TCP_CORK, &opt, sizeof(opt));
> +
> +	ret = do_write(s->fd, &hdr, sizeof(hdr));
> +	if (ret) {
> +		eprintf("failed to send a req, %m\n");
> +		return -EIO;
> +	}
> +
> +	if (wlen) {
> +		ret = do_writev(s->fd, iov, wlen, aio_req->iov_offset);
> +		if (ret) {
> +			eprintf("failed to send a data, %m\n");
> +			return -EIO;
> +		}
> +	}
> +        opt = 0;
> +        setsockopt(s->fd, SOL_TCP, TCP_CORK, &opt, sizeof(opt));
> +
> +	return 0;
> +}
> +
> +static int read_write_object(int fd, char *buf, uint64_t oid, int copies,
> +			     unsigned int datalen, uint64_t offset,
> +			     int write, int create)
> +{
> +	struct sd_obj_req hdr;
> +	struct sd_obj_rsp *rsp = (struct sd_obj_rsp *)&hdr;
> +	unsigned int wlen, rlen;
> +	int ret;
> +
> +	memset(&hdr, 0, sizeof(hdr));
> +
> +	if (write) {
> +		wlen = datalen;
> +		rlen = 0;
> +		hdr.flags = SD_FLAG_CMD_WRITE;
> +		if (create)
> +			hdr.opcode = SD_OP_CREATE_AND_WRITE_OBJ;
> +		else
> +			hdr.opcode = SD_OP_WRITE_OBJ;
> +	} else {
> +		wlen = 0;
> +		rlen = datalen;
> +		hdr.opcode = SD_OP_READ_OBJ;
> +	}
> +	hdr.oid = oid;
> +	hdr.data_length = datalen;
> +	hdr.offset = offset;
> +	hdr.copies = copies;
> +
> +	ret = do_req(fd, (struct sd_req *)&hdr, buf, &wlen, &rlen);
> +	if (ret) {
> +		eprintf("failed to send a request to the sheep\n");
> +		return -1;
> +	}
> +
> +	switch (rsp->result) {
> +	case SD_RES_SUCCESS:
> +		return 0;
> +	default:
> +		eprintf("%s\n", sd_strerror(rsp->result));
> +		return -1;
> +	}
> +}
> +
> +static int read_object(int fd, char *buf, uint64_t oid, int copies,
> +		       unsigned int datalen, uint64_t offset)
> +{
> +	return read_write_object(fd, buf, oid, copies, datalen, offset, 0, 0);
> +}
> +
> +static int write_object(int fd, char *buf, uint64_t oid, int copies,
> +			unsigned int datalen, uint64_t offset, int create)
> +{
> +	return read_write_object(fd, buf, oid, copies, datalen, offset, 1, create);
> +}
> +
> +/* TODO: error cleanups */
> +static int sd_open(BlockDriverState *bs, const char *filename, int flags)
> +{
> +	int ret, i, fd;
> +	uint32_t vid = 0;
> +	struct bdrv_sd_state *s = bs->opaque;
> +	char vdi[256];
> +	uint32_t snapid;
> +	int for_snapshot = 0;
> +	char *buf;
> +
> +	strstart(filename, "sheepdog:", (const char **)&filename);
> +
> +	buf = qemu_malloc(SD_INODE_SIZE);
> +	if (!buf) {
> +		eprintf("Failed to allocate memory\n");
> +		return -1;
> +	}
> +
> +	for (i = 0; i < MAX_AIO_REQS; i++) {
> +		s->aio_req_free[i] = &s->aio_req_list[i];
> +		s->aio_req_list[i].aiocb = NULL;
> +	}
> +	s->nr_aio_req_free = MAX_AIO_REQS;
> +
> +	memset(vdi, 0, sizeof(vdi));
> +	if (parse_vdiname(s, filename, vdi, sizeof(vdi), &snapid) < 0)
> +		goto out;
> +	s->fd = get_sheep_fd(s);
> +	if (s->fd < 0)
> +		return -1;
> +
> +	if (snapid != CURRENT_VDI_ID)
> +		for_snapshot = 1;
> +
> +	ret = find_vdi_name(s, vdi, snapid, &vid, for_snapshot);
> +	if (ret)
> +		goto out;
> +
> +	if (snapid)
> +		dprintf("%" PRIx32 " non current inode was open.\n", vid);
> +	else
> +		s->is_current = 1;
> +
> +	fd = connect_to_sdog(s->addr);

I wonder why you need to open another connection here instead of using
s->fd. This pattern repeats at least in the snapshot functions, so I'm
sure it's there for a reason. Maybe add a comment?

> +	if (fd < 0) {
> +		eprintf("failed to connect\n");
> +		goto out;
> +	}
> +
> +	ret = read_object(fd, buf, vid_to_vdi_oid(vid), 0, SD_INODE_SIZE, 0);
> +
> +	close(fd);
> +
> +	if (ret)
> +		goto out;
> +
> +	memcpy(&s->inode, buf, sizeof(s->inode));
> +	s->nr_dirty_data_oids = 0;
> +
> +	bs->total_sectors = s->inode.vdi_size >> 9;
> +	strncpy(s->name, vdi, sizeof(s->name));
> +	qemu_free(buf);
> +
> +	QLIST_INIT(&s->pending_head);
> +	return 0;
> +out:
> +	qemu_free(buf);
> +	return -1;
> +}
> +
> +static int do_sd_create(const char *addr, char *filename, char *tag,
> +			int64_t total_sectors, uint32_t base_vid,
> +			uint32_t *vdi_id, int snapshot)
> +{
> +	struct sd_vdi_req hdr;
> +	struct sd_vdi_rsp *rsp = (struct sd_vdi_rsp *)&hdr;
> +	int fd, ret;
> +	unsigned int wlen, rlen = 0;
> +	char buf[SD_MAX_VDI_LEN];
> +
> +	fd = connect_to_sdog(addr);
> +	if (fd < 0)
> +		return -1;
> +
> +	strncpy(buf, filename, SD_MAX_VDI_LEN);
> +
> +	memset(&hdr, 0, sizeof(hdr));
> +	hdr.opcode = SD_OP_NEW_VDI;
> +	hdr.base_vdi_id = base_vid;
> +
> +	wlen = SD_MAX_VDI_LEN;
> +
> +	hdr.flags = SD_FLAG_CMD_WRITE;
> +	hdr.snapid = snapshot;
> +
> +	hdr.data_length = wlen;
> +	hdr.vdi_size = total_sectors * 512;
> +
> +	ret = do_req(fd, (struct sd_req *)&hdr, buf, &wlen, &rlen);
> +
> +	close(fd);
> +
> +	if (ret)
> +		return -1;
> +
> +	if (rsp->result != SD_RES_SUCCESS) {
> +		eprintf("%s, %s\n", sd_strerror(rsp->result), filename);
> +		return -1;
> +	}
> +
> +	if (vdi_id)
> +		*vdi_id = rsp->vdi_id;
> +
> +	return 0;
> +}
> +
> +static int sd_create(const char *filename, QEMUOptionParameter *options)
> +{
> +	int ret;
> +	uint32_t vid = 0;
> +	int64_t total_sectors = 0;
> +	char *backing_file = NULL;
> +
> +	strstart(filename, "sheepdog:", (const char **)&filename);
> +
> +	while (options && options->name) {
> +		if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
> +			total_sectors = options->value.n / 512;
> +		} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
> +			backing_file = options->value.s;
> +		}
> +		options++;
> +	}
> +
> +	if (backing_file) {
> +		BlockDriverState bs;
> +		char vdi[SD_MAX_VDI_LEN];
> +		uint32_t snapid;
> +
> +		strstart(backing_file, "sheepdog:", (const char **)&backing_file);
> +		memset(&bs, 0, sizeof(bs));
> +
> +		bs.opaque = qemu_malloc(sizeof(struct bdrv_sd_state));
> +		if (!bs.opaque)
> +			return -1;
> +
> +		ret = sd_open(&bs, backing_file, 0);
> +		if (ret < 0)
> +			return -1;
> +
> +		if (parse_vdiname(bs.opaque, backing_file, vdi, sizeof(vdi), &snapid) < 0)
> +			return -1;
> +
> +		/* cannot clone from a current inode */
> +		if (snapid == CURRENT_VDI_ID)
> +			return -1;
> +
> +		ret = find_vdi_name(bs.opaque, vdi, snapid, &vid, 1);
> +		if (ret)
> +			return -1;
> +	}
> +
> +	return do_sd_create(NULL, (char *)filename, NULL, total_sectors, vid,
> +			    NULL, 0);
> +}
> +
> +static void sd_close(BlockDriverState *bs)
> +{
> +	struct bdrv_sd_state *s = bs->opaque;
> +	struct sd_vdi_req hdr;
> +	struct sd_vdi_rsp *rsp = (struct sd_vdi_rsp *)&hdr;
> +	unsigned int wlen, rlen = 0;
> +	int fd, ret;
> +
> +	dprintf("%s\n", s->name);
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0)
> +		return;
> +
> +	memset(&hdr, 0, sizeof(hdr));
> +
> +	hdr.opcode = SD_OP_RELEASE_VDI;
> +	wlen = strlen(s->name) + 1;
> +	hdr.data_length = wlen;
> +	hdr.flags = SD_FLAG_CMD_WRITE;
> +
> +	ret = do_req(fd, (struct sd_req *)&hdr, s->name, &wlen, &rlen);
> +
> +	close(fd);
> +
> +	if (!ret && rsp->result != SD_RES_SUCCESS &&
> +	    rsp->result != SD_RES_VDI_NOT_LOCKED)
> +		eprintf("%s, %s\n", sd_strerror(rsp->result), s->name);
> +
> +	close(s->fd);
> +	free(s->addr);
> +}
> +
> +static void sd_write_done(struct sd_aiocb *acb)
> +{
> +	int ret, i;
> +	struct bdrv_sd_state *s = acb->common.bs->opaque;
> +	struct iovec iov;
> +	struct aio_req *aio_req;
> +	uint32_t offset, data_len, mn, mx;
> +
> +	if (s->nr_dirty_data_oids) {
> +		mn = mx = s->dirty_data_oids[0];
> +		for (i = 0; i < s->nr_dirty_data_oids; i++) {
> +			if (mn > s->dirty_data_oids[i])
> +				mn = s->dirty_data_oids[i];
> +			if (mx < s->dirty_data_oids[i])
> +				mx = s->dirty_data_oids[i];
> +		}
> +		offset = sizeof(s->inode) - sizeof(s->inode.data_vdi_id) +
> +			mn * sizeof(s->inode.data_vdi_id[0]);
> +		data_len = (mx - mn + 1) * sizeof(s->inode.data_vdi_id[0]);
> +		s->nr_dirty_data_oids = 0;
> +
> +		iov.iov_base = &s->inode;
> +		iov.iov_len = sizeof(s->inode);
> +		aio_req = alloc_aio_req(s, acb, vid_to_vdi_oid(s->inode.vdi_id),
> +					data_len, offset, 0, 0, offset);
> +		if (!aio_req) {
> +			eprintf("too many requests\n");
> +			acb->ret = -EIO;
> +			goto out;
> +		}

Randomly failing requests is probably not a good idea. The guest might
decide that the disk/file system is broken and stop using it. Can't you
use a list like in AIOPool, so you can dynamically add new requests as
needed?

> +		ret = add_aio_request(s, aio_req, &iov, 1, 0, AIOCB_WRITE_UDATA);
> +		if (ret) {
> +			free_aio_req(s, aio_req);
> +			acb->ret = -EIO;
> +			goto out;
> +		}
> +
> +		acb->aio_done_func = sd_finish_aiocb;
> +		acb->aiocb_type = AIOCB_WRITE_UDATA;
> +		return;
> +	}
> +out:
> +	sd_finish_aiocb(acb);
> +}
> +
> +static int sd_create_branch(struct bdrv_sd_state *s)
> +{
> +	int ret, fd;
> +	uint32_t vid;
> +	char *buf;
> +
> +	dprintf("%" PRIx32 " is not current.\n", s->inode.vdi_id);
> +
> +	buf = qemu_malloc(SD_INODE_SIZE);
> +	if (!buf)
> +		return -1;
> +
> +	ret = do_sd_create(s->addr, s->name, NULL, s->inode.vdi_size >> 9,
> +			   s->inode.vdi_id, &vid, 1);
> +	if (ret)
> +		goto out;
> +
> +	dprintf("%" PRIx32 " is created.\n", vid);
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0) {
> +		eprintf("failed to connect\n");
> +		goto out;
> +	}
> +
> +	ret = read_object(fd, buf, vid_to_vdi_oid(vid), s->inode.nr_copies,
> +			  SD_INODE_SIZE, 0);
> +
> +	close(fd);
> +
> +	if (ret < 0)
> +		goto out;
> +
> +	memcpy(&s->inode, buf, sizeof(s->inode));
> +
> +	s->is_current = 1;
> +	ret = 0;
> +	dprintf("%" PRIx32 " was newly created.\n", s->inode.vdi_id);
> +
> +out:
> +	qemu_free(buf);
> +
> +	return ret;
> +}
> +
> +static void sd_readv_writev_bh_cb(void *p)
> +{
> +	struct sd_aiocb *acb = p;
> +	int ret = 0;
> +	unsigned long len, done = 0, total = acb->nb_sectors * 512;
> +	unsigned long idx = acb->sector_num * 512 / SD_DATA_OBJ_SIZE;
> +	uint64_t oid;
> +	uint64_t offset = (acb->sector_num * 512) % SD_DATA_OBJ_SIZE;
> +	struct bdrv_sd_state *s = acb->common.bs->opaque;
> +	struct sd_inode *inode = &s->inode;
> +	struct aio_req *aio_req;
> +
> +	qemu_bh_delete(acb->bh);
> +	acb->bh = NULL;
> +
> +	if (acb->aiocb_type == AIOCB_WRITE_UDATA && !s->is_current) {
> +		ret = sd_create_branch(s);
> +		if (ret) {
> +			acb->ret = -EIO;
> +			goto out;
> +		}
> +	}
> +
> +	while (done != total) {
> +		uint8_t flags = 0;
> +		uint64_t old_oid = 0;
> +		int create = 0;
> +
> +		oid = vid_to_data_oid(inode->data_vdi_id[idx], idx);
> +
> +		len = min_t(unsigned long, total - done, SD_DATA_OBJ_SIZE - offset);
> +
> +		if (!inode->data_vdi_id[idx]) {
> +			if (acb->aiocb_type == AIOCB_READ_UDATA)
> +				goto done;
> +
> +			create = 1;
> +		} else if (acb->aiocb_type == AIOCB_WRITE_UDATA
> +			   && !is_data_obj_writeable(inode, idx)) {
> +			create = 1;
> +			old_oid = oid;
> +			flags = SD_FLAG_CMD_COW;
> +		}
> +
> +		if (create) {
> +			dprintf("update ino (%" PRIu32") %"
> +				PRIu64 " %" PRIu64 " %" PRIu64 "\n",
> +				inode->vdi_id, oid,
> +				vid_to_data_oid(inode->data_vdi_id[idx], idx), idx);
> +			oid = vid_to_data_oid(inode->vdi_id, idx);
> +			dprintf("new oid %lx\n", oid);
> +		}
> +
> +		aio_req = alloc_aio_req(s, acb, oid, len, offset, flags,
> +					old_oid, done);
> +		if (!aio_req) {
> +			eprintf("too many requests\n");
> +			acb->ret = -EIO;
> +			goto out;
> +		}
> +
> +		if (create) {
> +			struct aio_req *areq;
> +			QLIST_FOREACH(areq, &s->pending_head, pending_siblings) {
> +				if (get_id_from_req(s, areq) == get_id_from_req(s, aio_req))
> +					continue;
> +				if (areq->oid == oid) {
> +					aio_req->flags = 0;
> +					aio_req->base_oid = 0;
> +					goto done;
> +				}
> +			}
> +		}
> +
> +		ret = add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov,
> +				      create, acb->aiocb_type);
> +		if (ret < 0) {
> +			eprintf("add_aio_request is faled\n");
> +			free_aio_req(s, aio_req);
> +			acb->ret = -EIO;
> +			goto out;
> +		}
> +	done:
> +		offset = 0;
> +		idx++;
> +		done += len;
> +	}
> +out:
> +	if (QLIST_EMPTY(&acb->aioreq_head))
> +		sd_finish_aiocb(acb);
> +}
> +
> +static BlockDriverAIOCB *sd_aio_writev(BlockDriverState *bs,
> +				       int64_t sector_num,
> +				       QEMUIOVector *qiov,
> +				       int nb_sectors,
> +				       BlockDriverCompletionFunc *cb,
> +				       void *opaque)
> +{
> +	struct sd_aiocb *acb;
> +
> +	acb = sd_aio_setup(bs, qiov, sector_num, nb_sectors, cb, opaque);
> +	acb->aio_done_func = sd_write_done;
> +	acb->aiocb_type = AIOCB_WRITE_UDATA;
> +
> +	sd_schedule_bh(sd_readv_writev_bh_cb, acb);
> +	return &acb->common;
> +}
> +
> +static BlockDriverAIOCB *sd_aio_readv(BlockDriverState *bs,
> +				      int64_t sector_num,
> +				      QEMUIOVector *qiov,
> +				      int nb_sectors,
> +				      BlockDriverCompletionFunc *cb,
> +				      void *opaque)
> +{
> +	struct sd_aiocb *acb;
> +	int i;
> +
> +	acb = sd_aio_setup(bs, qiov, sector_num, nb_sectors, cb, opaque);
> +	acb->aiocb_type = AIOCB_READ_UDATA;
> +	acb->aio_done_func = sd_finish_aiocb;
> +
> +	/*
> +	 * TODO: we can do better; we don't need to initialize
> +	 * blindly.
> +	 */
> +	for (i = 0; i < qiov->niov; i++)
> +		memset(qiov->iov[i].iov_base, 0, qiov->iov[i].iov_len);
> +
> +	sd_schedule_bh(sd_readv_writev_bh_cb, acb);
> +	return &acb->common;
> +}
> +
> +static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
> +{
> +	struct bdrv_sd_state *s = bs->opaque;
> +	int ret, fd;
> +	uint32_t new_vid;
> +	struct sd_inode *inode;
> +	unsigned int datalen;
> +	uint64_t offset;
> +
> +	dprintf("sn_info: name %s id_str %s s: name %s vm_state_size %d "
> +		"is_current %d\n", sn_info->name, sn_info->id_str,
> +		s->name, sn_info->vm_state_size, s->is_current);
> +
> +	if (!s->is_current) {
> +		eprintf("You can't create a snapshot of "
> +			"a non current VDI, %s (%" PRIu32 ").\n",
> +			s->name, s->inode.vdi_id);
> +
> +		return -1;
> +	}
> +
> +	dprintf("%s %s\n", sn_info->name, sn_info->id_str);
> +
> +	s->inode.vm_state_size = sn_info->vm_state_size;
> +	s->inode.vm_clock_nsec = sn_info->vm_clock_nsec;
> +	offset = 0;
> +	/* we don't need to read entire object */
> +	datalen = SD_INODE_SIZE - sizeof(s->inode.data_vdi_id);
> +
> +	/* refresh inode. */
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0) {
> +		ret = -EIO;
> +		goto cleanup;
> +	}
> +
> +	ret = write_object(fd, (char *)&s->inode, vid_to_vdi_oid(s->inode.vdi_id),
> +			   s->inode.nr_copies, datalen, offset, 0);
> +	if (ret < 0) {
> +		eprintf("failed to write snapshot's inode.\n");
> +		ret = -EIO;
> +		goto cleanup;
> +	}
> +
> +	ret = do_sd_create(s->addr, s->name, NULL, s->inode.vdi_size >> 9,
> +			   s->inode.vdi_id, &new_vid, 1);
> +	if (ret < 0) {
> +		eprintf("failed to create inode for snapshot. %m\n");
> +		ret = -EIO;
> +		goto cleanup;
> +	}
> +
> +	inode = (struct sd_inode *)qemu_malloc(datalen);
> +	if (!inode) {
> +		eprintf("failed to allocate memory for inode. %m\n");
> +		goto cleanup;
> +	}
> +
> +	ret = read_object(fd, (char *)inode, vid_to_vdi_oid(new_vid),
> +			  s->inode.nr_copies, datalen, offset);
> +
> +	close(fd);
> +
> +	if (ret < 0) {
> +		eprintf("failed to read new inode info. %m\n");
> +		ret = -EIO;
> +		goto cleanup;
> +	}
> +
> +	memcpy(&s->inode, inode, datalen);
> +	dprintf("s->inode: name %s snap_id %x oid %x\n",
> +		s->inode.name, s->inode.snap_id, s->inode.vdi_id);
> +
> +cleanup:
> +	close(fd);
> +	return ret;
> +}
> +
> +static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
> +{
> +	struct bdrv_sd_state *s = bs->opaque;
> +	struct bdrv_sd_state *old_s;
> +	char vdi[SD_MAX_VDI_LEN];
> +	char *buf = NULL;
> +	uint32_t vid;
> +	uint32_t snapid = 0;
> +	int ret = -ENOENT, fd;
> +
> +	old_s = qemu_malloc(sizeof(struct bdrv_sd_state));
> +	if (!old_s) {

qemu_malloc never returns NULL.

> +		eprintf("failed to allocate memory for old state. %m\n");
> +		goto out;
> +	}
> +
> +	memcpy(old_s, s, sizeof(struct bdrv_sd_state));
> +
> +	snapid = strtol(snapshot_id, NULL, 10);
> +	if (!snapid) {
> +		eprintf("Invalid snapshot_id\n");
> +		goto out;
> +	}
> +
> +	buf = qemu_malloc(SD_INODE_SIZE);
> +	if (!buf) {
> +		eprintf("Failed to allocate memory\n");
> +		goto out;
> +	}
> +	strncpy(vdi, s->name, sizeof(vdi));
> +	ret = find_vdi_name(s, vdi, snapid, &vid, 1);
> +	if (ret) {
> +		eprintf("Failed to find_vdi_name\n");
> +		ret = -ENOENT;
> +		goto out;
> +	}
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0) {
> +		eprintf("failed to connect\n");
> +		goto out;
> +	}
> +
> +	ret = read_object(fd, buf, vid_to_vdi_oid(vid), s->inode.nr_copies,
> +			  SD_INODE_SIZE, 0);
> +
> +	close(fd);
> +
> +	if (ret) {
> +		ret = -ENOENT;
> +		goto out;
> +	}
> +
> +	memcpy(&s->inode, buf, sizeof(s->inode));
> +
> +	if (!s->inode.vm_state_size) {
> +		eprintf("Invalid snapshot\n");
> +		ret = -ENOENT;
> +		goto out;
> +	}
> +
> +	s->is_current = 0;
> +
> +	qemu_free(buf);
> +	qemu_free(old_s);
> +
> +	return 0;
> +out:
> +	/* recover bdrv_sd_state */
> +	memcpy(s, old_s, sizeof(struct bdrv_sd_state));
> +	qemu_free(buf);
> +	qemu_free(old_s);
> +
> +	eprintf("failed to open. recover old bdrv_sd_state.\n");
> +
> +	return ret;
> +}
> +
> +static int sd_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
> +{
> +	/* FIXME: Delete specified snapshot id.  */
> +	return 0;
> +}

Ok, obviously there's something missing. ;-)

> +
> +#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
> +#define BITS_PER_BYTE		8
> +#define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
> +#define DECLARE_BITMAP(name,bits) \
> +	unsigned long name[BITS_TO_LONGS(bits)]
> +
> +#define BITS_PER_LONG (BITS_PER_BYTE * sizeof(long))
> +
> +static inline int test_bit(unsigned int nr, const unsigned long *addr)
> +{
> +	return ((1UL << (nr % BITS_PER_LONG)) &
> +		(((unsigned long *)addr)[nr / BITS_PER_LONG])) != 0;
> +}
> +
> +static int sd_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
> +{
> +	struct bdrv_sd_state *s = bs->opaque;
> +	struct sd_req req;
> +	int i, fd, nr = 1024, ret, max = BITS_TO_LONGS(SD_NR_VDIS) * sizeof(long);
> +	QEMUSnapshotInfo *sn_tab = NULL;
> +	unsigned wlen, rlen;
> +	int found = 0;
> +	static struct sd_inode inode;
> +	unsigned long *vdi_inuse;
> +	unsigned int start_nr;
> +
> +	vdi_inuse = qemu_malloc(max);
> +	if (!vdi_inuse)
> +		return 0;
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0)
> +		goto out;
> +
> +	rlen = max;
> +	wlen = 0;
> +
> +	memset(&req, 0, sizeof(req));
> +
> +	req.opcode = SD_OP_READ_VDIS;
> +	req.data_length = max;
> +
> +	ret = do_req(fd, (struct sd_req *)&req, vdi_inuse, &wlen, &rlen);
> +
> +	close(fd);
> +	if (ret)
> +		goto out;
> +
> +	sn_tab = qemu_mallocz(nr * sizeof(*sn_tab));
> +	if (!sn_tab)
> +		goto out;
> +
> +	start_nr = fnv_64a_buf(s->name, strlen(s->name), FNV1A_64_INIT) & (SD_NR_VDIS - 1);
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0) {
> +		eprintf("failed to connect\n");
> +		goto out;
> +	}
> +
> +	/* TODO: round up */
> +	for (i = start_nr; i < SD_NR_VDIS && found < nr; i++) {
> +		if (!test_bit(i, vdi_inuse))
> +			break;
> +
> +		/* we don't need to read entire object */
> +		ret = read_object(fd, (char *)&inode, vid_to_vdi_oid(i),
> +				  0, SD_INODE_SIZE - sizeof(inode.data_vdi_id), 0);
> +
> +		if (ret)
> +			continue;
> +
> +		if (!strcmp(inode.name, s->name) && inode.snap_ctime) {
> +			sn_tab[found].date_sec = inode.snap_ctime >> 32;
> +			sn_tab[found].date_nsec = inode.snap_ctime & 0xffffffff;
> +			sn_tab[found].vm_state_size = inode.vm_state_size;
> +			sn_tab[found].vm_clock_nsec = inode.vm_clock_nsec;
> +
> +			snprintf(sn_tab[found].id_str, sizeof(sn_tab[found].id_str), "%u",
> +				 inode.snap_id);
> +			found++;
> +		}
> +	}
> +
> +	close(fd);
> +out:
> +	*psn_tab = sn_tab;
> +
> +	qemu_free(vdi_inuse);
> +
> +	return found;
> +}
> +
> +static int do_load_save_vmstate(struct bdrv_sd_state *s, uint8_t *data,
> +				int64_t pos, int size, int load)
> +{
> +	int fd, create;
> +	int ret = 0;
> +	unsigned int data_len;
> +	uint64_t vmstate_oid;
> +	uint32_t vdi_index;
> +	uint64_t offset;
> +
> +	fd = connect_to_sdog(s->addr);
> +	if (fd < 0) {
> +		ret = -EIO;
> +		goto cleanup;
> +	}
> +
> +	while (size) {
> +		vdi_index = pos / SD_DATA_OBJ_SIZE;
> +		offset = pos % SD_DATA_OBJ_SIZE;
> +
> +		data_len = min_t(unsigned int, size, SD_DATA_OBJ_SIZE);
> +
> +		vmstate_oid = vid_to_vmstate_oid(s->inode.vdi_id, vdi_index);
> +
> +		create = (offset == 0);
> +		if (load)
> +			ret = read_object(fd, (char *)data, vmstate_oid,
> +					  s->inode.nr_copies, data_len, offset);
> +		else
> +			ret = write_object(fd, (char *)data, vmstate_oid,
> +					   s->inode.nr_copies, data_len, offset, create);
> +
> +		if (ret < 0) {
> +			eprintf("failed to save vmstate %m\n");
> +			ret = -EIO;
> +			goto cleanup;
> +		}
> +
> +		pos += data_len;
> +		size -= data_len;
> +		ret += data_len;
> +	}
> +cleanup:
> +	close(fd);
> +	return ret;
> +}
> +
> +static int sd_save_vmstate(BlockDriverState *bs, const uint8_t *data,
> +			   int64_t pos, int size)
> +{
> +	struct bdrv_sd_state *s = bs->opaque;
> +
> +	return do_load_save_vmstate(s, (uint8_t *)data, pos, size, 0);
> +}
> +
> +static int sd_load_vmstate(BlockDriverState *bs, uint8_t *data,
> +			   int64_t pos, int size)
> +{
> +	struct bdrv_sd_state *s = bs->opaque;
> +
> +	return do_load_save_vmstate(s, data, pos, size, 1);
> +}
> +
> +
> +static QEMUOptionParameter sd_create_options[] = {
> +	{
> +		.name = BLOCK_OPT_SIZE,
> +		.type = OPT_SIZE,
> +		.help = "Virtual disk size"
> +	},
> +	{
> +		.name = BLOCK_OPT_BACKING_FILE,
> +		.type = OPT_STRING,
> +		.help = "File name of a base image"
> +	},
> +	{ NULL }
> +};
> +
> +BlockDriver bdrv_sheepdog = {
> +	.format_name = "sheepdog",
> +	.protocol_name = "sheepdog",
> +	.instance_size = sizeof(struct bdrv_sd_state),
> +	.bdrv_file_open = sd_open,
> +	.bdrv_close = sd_close,
> +	.bdrv_create = sd_create,
> +
> +	.bdrv_aio_readv = sd_aio_readv,
> +	.bdrv_aio_writev = sd_aio_writev,
> +
> +	.bdrv_snapshot_create = sd_snapshot_create,
> +	.bdrv_snapshot_goto = sd_snapshot_goto,
> +	.bdrv_snapshot_delete = sd_snapshot_delete,
> +	.bdrv_snapshot_list = sd_snapshot_list,
> +
> +	.bdrv_save_vmstate = sd_save_vmstate,
> +	.bdrv_load_vmstate = sd_load_vmstate,
> +
> +	.create_options = sd_create_options,
> +};

Please align the = to the same column, at least in each block.

Kevin
MORITA Kazutaka - May 17, 2010, 10:34 a.m.
Hi,

Thank you very much for the reviewing!

At Fri, 14 May 2010 13:08:06 +0200,
Kevin Wolf wrote:

> > +
> > +struct sd_req {
> > +	uint8_t		proto_ver;
> > +	uint8_t		opcode;
> > +	uint16_t	flags;
> > +	uint32_t	epoch;
> > +	uint32_t        id;
> > +	uint32_t        data_length;
> > +	uint32_t	opcode_specific[8];
> > +};
> 
> CODING_STYLE says that structs should be typedefed and their names
> should be in CamelCase. So something like this:
> 
> typedef struct SheepdogReq {
>     ...
> } SheepdogReq;
> 
> (Or, if your prefer, SDReq; but with things like SDAIOCB I think it
> becomes hard to read)
> 

I see. I use Sheepdog as a prefix, like SheepdogReq.


> > +/*
> > +
> > +#undef eprintf
> > +#define eprintf(fmt, args...)						\
> > +do {									\
> > +	fprintf(stderr, "%s %d: " fmt, __func__, __LINE__, ##args);	\
> > +} while (0)
> 
> What about using error_report() instead of fprintf? Though it should be
> the same currently.
> 

Yes, using common helper functions is better.  I replaced all the
printf.


> > +
> > +	for (i = 0; i < ARRAY_SIZE(errors); ++i)
> > +		if (errors[i].err == err)
> > +			return errors[i].desc;
> 
> CODING_STYLE requires braces here.
> 

I fixed all the missing braces.


> > +
> > +	return "Invalid error code";
> > +}
> > +
> > +static inline int before(uint32_t seq1, uint32_t seq2)
> > +{
> > +        return (int32_t)(seq1 - seq2) < 0;
> > +}
> > +
> > +static inline int after(uint32_t seq1, uint32_t seq2)
> > +{
> > +	return (int32_t)(seq2 - seq1) < 0;
> > +}
> 
> These functions look strange... Is the difference to seq1 < seq2 that
> the cast introduces intentional? (after(0x0, 0xabcdefff) == 1)
> 
> If yes, why is this useful? This needs a comment. If no, why even bother
> to have this function instead of directly using < or > ?
> 

These functions are used to compare sequential numbers which can be
wrap-around. For example, linux/net/tcp.h in the linux kernel.

Anyway, sheepdog doesn't use these functions, so I removed them.


> > +	if (snapid)
> > +		dprintf("%" PRIx32 " non current inode was open.\n", vid);
> > +	else
> > +		s->is_current = 1;
> > +
> > +	fd = connect_to_sdog(s->addr);
> 
> I wonder why you need to open another connection here instead of using
> s->fd. This pattern repeats at least in the snapshot functions, so I'm
> sure it's there for a reason. Maybe add a comment?
> 

We can use s->fd only for aio read/write operations.  It is because
the block driver may be during waiting response from the server, so we
cannot send other requests to the discriptor to avoid receiving wrong
data.

I added the comment to get_sheep_fd().


> > +
> > +		iov.iov_base = &s->inode;
> > +		iov.iov_len = sizeof(s->inode);
> > +		aio_req = alloc_aio_req(s, acb, vid_to_vdi_oid(s->inode.vdi_id),
> > +					data_len, offset, 0, 0, offset);
> > +		if (!aio_req) {
> > +			eprintf("too many requests\n");
> > +			acb->ret = -EIO;
> > +			goto out;
> > +		}
> 
> Randomly failing requests is probably not a good idea. The guest might
> decide that the disk/file system is broken and stop using it. Can't you
> use a list like in AIOPool, so you can dynamically add new requests as
> needed?
> 

I agree.  In the v3 patch, AIO requests are allocated dynamically, and
all the requests are linked to the outstanding_aio_head in the
BDRVSheepdogState.


> > +
> > +static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
> > +{
> > +	struct bdrv_sd_state *s = bs->opaque;
> > +	struct bdrv_sd_state *old_s;
> > +	char vdi[SD_MAX_VDI_LEN];
> > +	char *buf = NULL;
> > +	uint32_t vid;
> > +	uint32_t snapid = 0;
> > +	int ret = -ENOENT, fd;
> > +
> > +	old_s = qemu_malloc(sizeof(struct bdrv_sd_state));
> > +	if (!old_s) {
> 
> qemu_malloc never returns NULL.
> 

I removed all the NULL checks.


> > +
> > +BlockDriver bdrv_sheepdog = {
> > +	.format_name = "sheepdog",
> > +	.protocol_name = "sheepdog",
> > +	.instance_size = sizeof(struct bdrv_sd_state),
> > +	.bdrv_file_open = sd_open,
> > +	.bdrv_close = sd_close,
> > +	.bdrv_create = sd_create,
> > +
> > +	.bdrv_aio_readv = sd_aio_readv,
> > +	.bdrv_aio_writev = sd_aio_writev,
> > +
> > +	.bdrv_snapshot_create = sd_snapshot_create,
> > +	.bdrv_snapshot_goto = sd_snapshot_goto,
> > +	.bdrv_snapshot_delete = sd_snapshot_delete,
> > +	.bdrv_snapshot_list = sd_snapshot_list,
> > +
> > +	.bdrv_save_vmstate = sd_save_vmstate,
> > +	.bdrv_load_vmstate = sd_load_vmstate,
> > +
> > +	.create_options = sd_create_options,
> > +};
> 
> Please align the = to the same column, at least in each block.
> 

I have aligned in the v3 patch.


Thanks,

Kazutaka

Patch

diff --git a/Makefile.objs b/Makefile.objs
index ecdd53e..6edbc57 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -14,7 +14,7 @@  block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 
 block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat.o
 block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
-block-nested-y += parallels.o nbd.o blkdebug.o
+block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o
 block-nested-$(CONFIG_WIN32) += raw-win32.o
 block-nested-$(CONFIG_POSIX) += raw-posix.o
 block-nested-$(CONFIG_CURL) += curl.o
diff --git a/block/sheepdog.c b/block/sheepdog.c
new file mode 100644
index 0000000..adf3a71
--- /dev/null
+++ b/block/sheepdog.c
@@ -0,0 +1,1831 @@ 
+/*
+ * Copyright (C) 2009-2010 Nippon Telegraph and Telephone Corporation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <netdb.h>
+#include <netinet/tcp.h>
+
+#include "qemu-common.h"
+#include "block_int.h"
+
+#define SD_PROTO_VER 0x01
+
+#define SD_DEFAULT_ADDR "localhost:7000"
+
+#define SD_OP_CREATE_AND_WRITE_OBJ  0x01
+#define SD_OP_READ_OBJ       0x02
+#define SD_OP_WRITE_OBJ      0x03
+
+#define SD_OP_NEW_VDI        0x11
+#define SD_OP_LOCK_VDI       0x12
+#define SD_OP_RELEASE_VDI    0x13
+#define SD_OP_GET_VDI_INFO   0x14
+#define SD_OP_READ_VDIS      0x15
+
+#define SD_FLAG_CMD_WRITE    0x01
+#define SD_FLAG_CMD_COW      0x02
+
+#define SD_RES_SUCCESS       0x00 /* Success */
+#define SD_RES_UNKNOWN       0x01 /* Unknown error */
+#define SD_RES_NO_OBJ        0x02 /* No object found */
+#define SD_RES_EIO           0x03 /* I/O error */
+#define SD_RES_VDI_EXIST     0x04 /* Vdi exists already */
+#define SD_RES_INVALID_PARMS 0x05 /* Invalid parameters */
+#define SD_RES_SYSTEM_ERROR  0x06 /* System error */
+#define SD_RES_VDI_LOCKED    0x07 /* Vdi is locked */
+#define SD_RES_NO_VDI        0x08 /* No vdi found */
+#define SD_RES_NO_BASE_VDI   0x09 /* No base vdi found */
+#define SD_RES_VDI_READ      0x0A /* Cannot read requested vdi */
+#define SD_RES_VDI_WRITE     0x0B /* Cannot write requested vdi */
+#define SD_RES_BASE_VDI_READ 0x0C /* Cannot read base vdi */
+#define SD_RES_BASE_VDI_WRITE   0x0D /* Cannot write base vdi */
+#define SD_RES_NO_TAG        0x0E /* Requested tag is not found */
+#define SD_RES_STARTUP       0x0F /* Sheepdog is on starting up */
+#define SD_RES_VDI_NOT_LOCKED   0x10 /* Vdi is not locked */
+#define SD_RES_SHUTDOWN      0x11 /* Sheepdog is shutting down */
+#define SD_RES_NO_MEM        0x12 /* Cannot allocate memory */
+#define SD_RES_FULL_VDI      0x13 /* we already have the maximum vdis */
+#define SD_RES_VER_MISMATCH  0x14 /* Protocol version mismatch */
+#define SD_RES_NO_SPACE      0x15 /* Server has no room for new objects */
+#define SD_RES_WAIT_FOR_FORMAT  0x16 /* Sheepdog is waiting for a format operation */
+#define SD_RES_WAIT_FOR_JOIN    0x17 /* Sheepdog is waiting for other nodes joining */
+#define SD_RES_JOIN_FAILED   0x18 /* Target node had failed to join sheepdog */
+
+/*
+ * Object ID rules
+ *
+ *  0 - 19 (20 bits): data object space
+ * 20 - 31 (12 bits): reserved data object space
+ * 32 - 55 (24 bits): vdi object space
+ * 56 - 59 ( 4 bits): reserved vdi object space
+ * 60 - 63 ( 4 bits): object type indentifier space
+ */
+
+#define VDI_SPACE_SHIFT   32
+#define VDI_BIT (UINT64_C(1) << 63)
+#define VMSTATE_BIT (UINT64_C(1) << 62)
+#define MAX_DATA_OBJS (1ULL << 20)
+#define MAX_CHILDREN 1024
+#define SD_MAX_VDI_LEN 256
+#define SD_NR_VDIS   (1U << 24)
+#define SD_DATA_OBJ_SIZE (UINT64_C(1) << 22)
+
+#define SD_INODE_SIZE (sizeof(struct sd_inode))
+#define CURRENT_VDI_ID 0
+
+struct sd_req {
+	uint8_t		proto_ver;
+	uint8_t		opcode;
+	uint16_t	flags;
+	uint32_t	epoch;
+	uint32_t        id;
+	uint32_t        data_length;
+	uint32_t	opcode_specific[8];
+};
+
+struct sd_rsp {
+	uint8_t		proto_ver;
+	uint8_t		opcode;
+	uint16_t	flags;
+	uint32_t	epoch;
+	uint32_t        id;
+	uint32_t        data_length;
+	uint32_t        result;
+	uint32_t	opcode_specific[7];
+};
+
+struct sd_obj_req {
+	uint8_t		proto_ver;
+	uint8_t		opcode;
+	uint16_t	flags;
+	uint32_t	epoch;
+	uint32_t        id;
+	uint32_t        data_length;
+	uint64_t        oid;
+	uint64_t        cow_oid;
+	uint32_t        copies;
+	uint32_t        rsvd;
+	uint64_t        offset;
+};
+
+struct sd_obj_rsp {
+	uint8_t		proto_ver;
+	uint8_t		opcode;
+	uint16_t	flags;
+	uint32_t	epoch;
+	uint32_t        id;
+	uint32_t        data_length;
+	uint32_t        result;
+	uint32_t        copies;
+	uint32_t        pad[6];
+};
+
+struct sd_vdi_req {
+	uint8_t		proto_ver;
+	uint8_t		opcode;
+	uint16_t	flags;
+	uint32_t	epoch;
+	uint32_t        id;
+	uint32_t        data_length;
+	uint64_t	vdi_size;
+	uint32_t        base_vdi_id;
+	uint32_t        copies;
+	uint32_t        snapid;
+	uint32_t        pad[3];
+};
+
+struct sd_vdi_rsp {
+	uint8_t		proto_ver;
+	uint8_t		opcode;
+	uint16_t	flags;
+	uint32_t	epoch;
+	uint32_t        id;
+	uint32_t        data_length;
+	uint32_t        result;
+	uint32_t        rsvd;
+	uint32_t        vdi_id;
+	uint32_t        pad[5];
+};
+
+struct sd_inode {
+	char name[SD_MAX_VDI_LEN];
+	uint64_t ctime;
+	uint64_t snap_ctime;
+	uint64_t vm_clock_nsec;
+	uint64_t vdi_size;
+	uint64_t vm_state_size;
+	uint16_t copy_policy;
+	uint8_t  nr_copies;
+	uint8_t  block_size_shift;
+	uint32_t snap_id;
+	uint32_t vdi_id;
+	uint32_t parent_vdi_id;
+	uint32_t child_vdi_id[MAX_CHILDREN];
+	uint32_t data_vdi_id[MAX_DATA_OBJS];
+};
+
+/*
+ * 64 bit FNV-1a non-zero initial basis
+ */
+#define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
+
+/*
+ * 64 bit Fowler/Noll/Vo FNV-1a hash code
+ */
+static inline uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval)
+{
+        unsigned char *bp = (unsigned char *) buf;
+        unsigned char *be = bp + len;
+        while (bp < be) {
+                hval ^= (uint64_t) *bp++;
+                hval += (hval << 1) + (hval << 4) + (hval << 5) +
+                        (hval << 7) + (hval << 8) + (hval << 40);
+        }
+        return hval;
+}
+
+static inline int is_data_obj_writeable(struct sd_inode *inode, unsigned int idx)
+{
+	return inode->vdi_id == inode->data_vdi_id[idx];
+}
+
+static inline int is_data_obj(uint64_t oid)
+{
+	return !(VDI_BIT & oid);
+}
+
+static inline uint64_t data_oid_to_idx(uint64_t oid)
+{
+	return oid & (MAX_DATA_OBJS - 1);
+}
+
+static inline uint64_t vid_to_vdi_oid(uint32_t vid)
+{
+	return VDI_BIT | ((uint64_t)vid << VDI_SPACE_SHIFT);
+}
+
+static inline uint64_t vid_to_vmstate_oid(uint32_t vid, uint32_t idx)
+{
+	return VMSTATE_BIT | ((uint64_t)vid << VDI_SPACE_SHIFT) | idx;
+}
+
+static inline uint64_t vid_to_data_oid(uint32_t vid, uint32_t idx)
+{
+	return ((uint64_t)vid << VDI_SPACE_SHIFT) | idx;
+}
+
+#undef eprintf
+#define eprintf(fmt, args...)						\
+do {									\
+	fprintf(stderr, "%s %d: " fmt, __func__, __LINE__, ##args);	\
+} while (0)
+
+#undef dprintf
+#ifdef DEBUG_SDOG
+#define dprintf(fmt, args...)						\
+do {									\
+	fprintf(stdout, "%s %d: " fmt, __func__, __LINE__, ##args);	\
+} while (0)
+#else
+#define dprintf(fmt, args...)
+#endif
+
+#define min_t(type, x, y) ({			\
+	type __min1 = (x);			\
+	type __min2 = (y);			\
+	__min1 < __min2 ? __min1: __min2; })
+
+struct aio_req {
+	struct sd_aiocb *aiocb;
+	unsigned int iov_offset;
+
+	uint64_t oid;
+	uint64_t base_oid;
+	uint64_t offset;
+	unsigned int data_len;
+	uint8_t flags;
+
+	QLIST_ENTRY(aio_req) pending_siblings;
+	QLIST_ENTRY(aio_req) aioreq_siblings;
+};
+
+enum aiocb_state {
+	AIOCB_WRITE_UDATA,
+	AIOCB_READ_UDATA,
+};
+
+struct sd_aiocb {
+	BlockDriverAIOCB common;
+
+	QEMUIOVector *qiov;
+
+	int64_t sector_num;
+	int nb_sectors;
+
+	int ret;
+	enum aiocb_state aiocb_type;
+
+	QEMUBH *bh;
+	void (*aio_done_func)(struct sd_aiocb *);
+
+	int canceled;
+
+	QLIST_HEAD(aioreq_head, aio_req) aioreq_head;
+};
+
+#define MAX_AIO_REQS 4096
+
+struct bdrv_sd_state {
+	struct sd_inode inode;
+
+	int nr_dirty_data_oids;
+	uint32_t dirty_data_oids[MAX_AIO_REQS];
+
+	char name[SD_MAX_VDI_LEN];
+	int is_current;
+
+	char *addr;
+	int fd;
+
+	struct aio_req aio_req_list[MAX_AIO_REQS];
+	struct aio_req *aio_req_free[MAX_AIO_REQS];
+	int nr_aio_req_free;
+
+	QLIST_HEAD(pending_head, aio_req) pending_head;
+};
+
+static const char * sd_strerror(int err)
+{
+	int i;
+
+	static const struct {
+		int err;
+		const char *desc;
+	} errors[] = {
+		{SD_RES_SUCCESS, "Success"},
+		{SD_RES_UNKNOWN, "Unknown error"},
+		{SD_RES_NO_OBJ, "No object found"},
+		{SD_RES_EIO, "I/O error"},
+		{SD_RES_VDI_EXIST, "VDI exists already"},
+		{SD_RES_INVALID_PARMS, "Invalid parameters"},
+		{SD_RES_SYSTEM_ERROR, "System error"},
+		{SD_RES_VDI_LOCKED, "VDI is already locked"},
+		{SD_RES_NO_VDI, "No vdi found"},
+		{SD_RES_NO_BASE_VDI, "No base VDI found"},
+		{SD_RES_VDI_READ, "Failed read the requested VDI"},
+		{SD_RES_VDI_WRITE, "Failed to write the requested VDI"},
+		{SD_RES_BASE_VDI_READ, "Failed to read the base VDI"},
+		{SD_RES_BASE_VDI_WRITE, "Failed to write the base VDI"},
+		{SD_RES_NO_TAG, "Failed to find the requested tag"},
+		{SD_RES_STARTUP, "The system is still booting"},
+		{SD_RES_VDI_NOT_LOCKED, "VDI isn't locked"},
+		{SD_RES_SHUTDOWN, "The system is shutting down"},
+		{SD_RES_NO_MEM, "Out of memory on the server"},
+		{SD_RES_FULL_VDI, "We already have the maximum vdis"},
+		{SD_RES_VER_MISMATCH, "Protocol version mismatch"},
+		{SD_RES_NO_SPACE, "Server has no space for new objects"},
+		{SD_RES_WAIT_FOR_FORMAT, "Sheepdog is waiting for a format operation"},
+		{SD_RES_WAIT_FOR_JOIN, "Sheepdog is waiting for other nodes joining"},
+		{SD_RES_JOIN_FAILED, "Target node had failed to join sheepdog"},
+	};
+
+	for (i = 0; i < ARRAY_SIZE(errors); ++i)
+		if (errors[i].err == err)
+			return errors[i].desc;
+
+	return "Invalid error code";
+}
+
+static inline int before(uint32_t seq1, uint32_t seq2)
+{
+        return (int32_t)(seq1 - seq2) < 0;
+}
+
+static inline int after(uint32_t seq1, uint32_t seq2)
+{
+	return (int32_t)(seq2 - seq1) < 0;
+}
+
+static inline struct aio_req *alloc_aio_req(struct bdrv_sd_state *s,
+					    struct sd_aiocb *acb,
+					    uint64_t oid, unsigned int data_len,
+					    uint64_t offset, uint8_t flags,
+					    uint64_t base_oid,
+					    unsigned int iov_offset)
+{
+	struct aio_req *aio_req;
+
+	if (!s->nr_aio_req_free)
+		return NULL;
+
+	aio_req = s->aio_req_free[--s->nr_aio_req_free];
+	aio_req->aiocb = acb;
+	aio_req->iov_offset = iov_offset;
+	aio_req->oid = oid;
+	aio_req->base_oid = base_oid;
+	aio_req->offset = offset;
+	aio_req->data_len = data_len;
+	aio_req->flags = flags;
+
+	QLIST_INSERT_HEAD(&s->pending_head, aio_req, pending_siblings);
+	QLIST_INSERT_HEAD(&acb->aioreq_head, aio_req, aioreq_siblings);
+
+	return aio_req;
+}
+
+static inline int free_aio_req(struct bdrv_sd_state *s, struct aio_req *aio_req)
+{
+	struct sd_aiocb *acb = aio_req->aiocb;
+	QLIST_REMOVE(aio_req, pending_siblings);
+	QLIST_REMOVE(aio_req, aioreq_siblings);
+	aio_req->aiocb = NULL;
+	s->aio_req_free[s->nr_aio_req_free++] = aio_req;
+
+	return !QLIST_EMPTY(&acb->aioreq_head);
+}
+
+static inline int nr_outstanding_aio_req(struct bdrv_sd_state *s)
+{
+	return MAX_AIO_REQS - s->nr_aio_req_free;
+}
+
+static inline int get_id_from_req(struct bdrv_sd_state *s, struct aio_req *aio_req)
+{
+	return aio_req - s->aio_req_list;
+}
+
+static inline struct aio_req *get_req_from_id(struct bdrv_sd_state *s, int id)
+{
+	return s->aio_req_list + id;
+}
+
+static void sd_finish_aiocb(struct sd_aiocb *acb)
+{
+	if (!acb->canceled)
+		acb->common.cb(acb->common.opaque, acb->ret);
+	qemu_aio_release(acb);
+}
+
+static void sd_aio_cancel(BlockDriverAIOCB *blockacb)
+{
+	struct sd_aiocb *acb = (struct sd_aiocb *)blockacb;
+
+	acb->canceled = 1;
+}
+
+static AIOPool sd_aio_pool = {
+	.aiocb_size = sizeof(struct sd_aiocb),
+	.cancel = sd_aio_cancel,
+};
+
+static struct sd_aiocb *sd_aio_setup(BlockDriverState *bs, QEMUIOVector *qiov,
+				     int64_t sector_num, int nb_sectors,
+				     BlockDriverCompletionFunc *cb,
+				     void *opaque)
+{
+	struct sd_aiocb *acb;
+
+	acb = qemu_aio_get(&sd_aio_pool, bs, cb, opaque);
+
+	acb->qiov = qiov;
+
+	acb->sector_num = sector_num;
+	acb->nb_sectors = nb_sectors;
+
+	acb->aio_done_func = NULL;
+	acb->canceled = 0;
+	acb->bh = NULL;
+	acb->ret = 0;
+	QLIST_INIT(&acb->aioreq_head);
+	return acb;
+}
+
+static int sd_schedule_bh(QEMUBHFunc *cb, struct sd_aiocb *acb)
+{
+	if (acb->bh) {
+		eprintf("bug: %d %d\n", acb->aiocb_type, acb->aiocb_type);
+		return -EIO;
+	}
+
+	acb->bh = qemu_bh_new(cb, acb);
+	if (!acb->bh) {
+		eprintf("oom: %d %d\n", acb->aiocb_type, acb->aiocb_type);
+		return -EIO;
+	}
+
+	qemu_bh_schedule(acb->bh);
+
+	return 0;
+}
+
+static int do_send_recv(int sockfd, struct iovec *iov, int len, int offset,
+			int write)
+{
+	struct msghdr msg;
+	int ret, diff;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.msg_iov = iov;
+	msg.msg_iovlen = 1;
+
+	len += offset;
+
+	while (iov->iov_len < len) {
+		len -= iov->iov_len;
+
+		iov++;
+		msg.msg_iovlen++;
+	}
+
+	diff = iov->iov_len - len;
+	iov->iov_len -= diff;
+
+	while (msg.msg_iov->iov_len <= offset) {
+		offset -= msg.msg_iov->iov_len;
+
+		msg.msg_iov++;
+		msg.msg_iovlen--;
+	}
+
+	msg.msg_iov->iov_base = (char *) msg.msg_iov->iov_base + offset;
+	msg.msg_iov->iov_len -= offset;
+
+	if (write)
+		ret = sendmsg(sockfd, &msg, 0);
+	else
+		ret = recvmsg(sockfd, &msg, MSG_WAITALL);
+
+	msg.msg_iov->iov_base = (char *) msg.msg_iov->iov_base - offset;
+	msg.msg_iov->iov_len += offset;
+
+	iov->iov_len += diff;
+	return ret;
+}
+
+static int connect_to_sdog(const char *addr)
+{
+	char buf[64];
+	char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
+	char name[256], *p;
+	int fd, ret;
+	struct addrinfo hints, *res, *res0;
+	int port = 0;
+
+	if (!addr)
+		addr = SD_DEFAULT_ADDR;
+
+	strcpy(name, addr);
+
+	p = name;
+	while (*p) {
+		if (*p == ':') {
+			*p++ = '\0';
+			break;
+		} else
+			p++;
+	}
+
+	if (*p == '\0') {
+		eprintf("cannot find a port number, %s\n", name);
+		return -1;
+	}
+	port = strtol(p, NULL, 10);
+	if (port == 0) {
+		eprintf("invalid port number, %s\n", p);
+		return -1;
+	}
+
+	memset(&hints, 0, sizeof(hints));
+	snprintf(buf, sizeof(buf), "%d", port);
+
+	hints.ai_socktype = SOCK_STREAM;
+
+	ret = getaddrinfo(name, buf, &hints, &res0);
+	if (ret) {
+		eprintf("unable to get address info %s, %m\n", name);
+		return -1;
+	}
+
+	for (res = res0; res; res = res->ai_next) {
+		ret = getnameinfo(res->ai_addr, res->ai_addrlen,
+				  hbuf, sizeof(hbuf), sbuf, sizeof(sbuf),
+				  NI_NUMERICHOST | NI_NUMERICSERV);
+		if (ret)
+			continue;
+
+		fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+		if (fd < 0)
+			continue;
+
+reconnect:
+		ret = connect(fd, res->ai_addr, res->ai_addrlen);
+		if (ret < 0) {
+			if (errno == EINTR)
+				goto reconnect;
+			break;
+		}
+
+		dprintf("connected to %s:%d\n", name, port);
+		goto success;
+	}
+	fd = -1;
+	eprintf("failed connect to %s:%d\n", name, port);
+success:
+	freeaddrinfo(res0);
+	return fd;
+}
+
+static int do_readv_writev(int sockfd, struct iovec *iov, int len,
+			   int iov_offset, int write)
+{
+	int ret;
+again:
+	ret = do_send_recv(sockfd, iov, len, iov_offset, write);
+	if (ret < 0) {
+		if (errno == EINTR || errno == EAGAIN)
+			goto again;
+		eprintf("failed to recv a rsp, %m\n");
+		return 1;
+	}
+
+	iov_offset += ret;
+	len -= ret;
+	if (len)
+		goto again;
+
+	return 0;
+}
+
+static int do_readv(int sockfd, struct iovec *iov, int len, int iov_offset)
+{
+	return do_readv_writev(sockfd, iov, len, iov_offset, 0);
+}
+
+static int do_writev(int sockfd, struct iovec *iov, int len, int iov_offset)
+{
+	return do_readv_writev(sockfd, iov, len, iov_offset, 1);
+}
+
+static int do_read_write(int sockfd, void *buf, int len, int write)
+{
+	struct iovec iov;
+
+	iov.iov_base = buf;
+	iov.iov_len = len;
+
+	return do_readv_writev(sockfd, &iov, len, 0, write);
+}
+
+static int do_read(int sockfd, void *buf, int len)
+{
+	return do_read_write(sockfd, buf, len, 0);
+}
+
+static int do_write(int sockfd, void *buf, int len)
+{
+	return do_read_write(sockfd, buf, len, 1);
+}
+
+static int send_req(int sockfd, struct sd_req *hdr, void *data,
+		    unsigned int *wlen)
+{
+	int ret;
+	struct iovec iov[2];
+
+	iov[0].iov_base = hdr;
+	iov[0].iov_len = sizeof(*hdr);
+
+	if (*wlen) {
+		iov[1].iov_base = data;
+		iov[1].iov_len = *wlen;
+	}
+
+	ret = do_writev(sockfd, iov, sizeof(*hdr) + *wlen, 0);
+	if (ret) {
+		eprintf("failed to send a req, %m\n");
+		ret = -1;
+	}
+
+	return ret;
+}
+
+static int do_req(int sockfd, struct sd_req *hdr, void *data,
+		  unsigned int *wlen, unsigned int *rlen)
+{
+	int ret;
+
+	ret = send_req(sockfd, hdr, data, wlen);
+	if (ret) {
+		ret = -1;
+		goto out;
+	}
+
+	ret = do_read(sockfd, hdr, sizeof(*hdr));
+	if (ret) {
+		eprintf("failed to get a rsp, %m\n");
+		ret = -1;
+		goto out;
+	}
+
+	if (*rlen > hdr->data_length)
+		*rlen = hdr->data_length;
+
+	if (*rlen) {
+		ret = do_read(sockfd, data, *rlen);
+		if (ret) {
+			eprintf("failed to get the data, %m\n");
+			ret = -1;
+			goto out;
+		}
+	}
+	ret = 0;
+out:
+	return ret;
+}
+
+static int add_aio_request(struct bdrv_sd_state *s, struct aio_req *aio_req,
+			   struct iovec *iov, int niov, int create,
+			   enum aiocb_state aiocb_type);
+
+static void send_pending_req(struct bdrv_sd_state *s, uint64_t oid, uint32_t id)
+{
+	struct aio_req *aio_req, *next;
+	struct sd_aiocb *acb;
+	int ret;
+
+	QLIST_FOREACH_SAFE(aio_req, &s->pending_head, pending_siblings, next) {
+		if (id == get_id_from_req(s, aio_req))
+			continue;
+		if (aio_req->oid != oid)
+			continue;
+
+		acb = aio_req->aiocb;
+		ret = add_aio_request(s, aio_req, acb->qiov->iov,
+				      acb->qiov->niov, 0, acb->aiocb_type);
+		if (ret < 0) {
+			eprintf("add_aio_request is faled\n");
+			free_aio_req(s, aio_req);
+			if (QLIST_EMPTY(&acb->aioreq_head))
+				sd_finish_aiocb(acb);
+		}
+	}
+}
+
+static void aio_read_response(void *opaque)
+{
+	struct sd_obj_req hdr;
+	struct sd_obj_rsp *rsp = (struct sd_obj_rsp *)&hdr;
+	struct bdrv_sd_state *s = (struct bdrv_sd_state *)opaque;
+	int fd = s->fd;
+	int ret;
+	struct aio_req *aio_req;
+	struct sd_aiocb *acb;
+	int rest;
+	unsigned long idx;
+
+	if (!nr_outstanding_aio_req(s))
+		return;
+
+	ret = do_read(fd, (void *)rsp, sizeof(*rsp));
+	if (ret) {
+		eprintf("failed to get the header, %m\n");
+		return;
+	}
+
+	aio_req = get_req_from_id(s, rsp->id);
+	acb = aio_req->aiocb;
+
+	switch (acb->aiocb_type) {
+	case AIOCB_WRITE_UDATA:
+		if (!is_data_obj(aio_req->oid))
+			break;
+		idx = data_oid_to_idx(aio_req->oid);
+
+		if (s->inode.data_vdi_id[idx] != s->inode.vdi_id) {
+			s->inode.data_vdi_id[idx] = s->inode.vdi_id;
+			s->dirty_data_oids[s->nr_dirty_data_oids++] = idx;
+
+			send_pending_req(s, vid_to_data_oid(s->inode.vdi_id, idx),
+					 rsp->id);
+		}
+		break;
+	case AIOCB_READ_UDATA:
+		ret = do_readv(fd, acb->qiov->iov, rsp->data_length,
+			       aio_req->iov_offset);
+		if (ret) {
+			eprintf("failed to get the data, %m\n");
+			return;
+		}
+		break;
+	}
+
+	if (rsp->result != SD_RES_SUCCESS) {
+		acb->ret = -EIO;
+		eprintf("%s\n", sd_strerror(rsp->result));
+	}
+
+	rest = free_aio_req(s, aio_req);
+	if (!rest)
+		acb->aio_done_func(acb);
+}
+
+static int aio_flush_request(void *opaque)
+{
+	return nr_outstanding_aio_req((struct bdrv_sd_state *)opaque);
+}
+
+static int set_nonblocking(int fd)
+{
+	int ret;
+
+	ret = fcntl(fd, F_GETFL);
+	if (ret < 0) {
+		eprintf("can't fcntl (F_GETFL), %m\n");
+		close(fd);
+	} else {
+		ret = fcntl(fd, F_SETFL, ret | O_NONBLOCK);
+		if (ret < 0)
+			eprintf("can't fcntl (O_NONBLOCK), %m\n");
+	}
+
+	return ret;
+}
+
+static int set_nodelay(int fd)
+{
+	int ret, opt;
+
+	opt = 1;
+	ret = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
+	return ret;
+}
+
+static int get_sheep_fd(struct bdrv_sd_state *s)
+{
+	int ret, fd;
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		eprintf("%m\n");
+		return -1;
+	}
+
+	ret = set_nonblocking(fd);
+	if (ret) {
+		eprintf("%m\n");
+		close(fd);
+		return -1;
+	}
+
+	ret = set_nodelay(fd);
+	if (ret) {
+		eprintf("%m\n");
+		close(fd);
+		return -1;
+	}
+
+	qemu_aio_set_fd_handler(fd, aio_read_response, NULL, aio_flush_request,
+				NULL, s);
+	s->fd = fd;
+
+	return fd;
+}
+
+static int parse_vdiname(struct bdrv_sd_state *s, const char *filename,
+			 char *vdi, int vdi_len, uint32_t *snapid)
+{
+	char *p, *q;
+	int nr_sep;
+
+	p = q = strdup(filename);
+
+	if (!p)
+		return 1;
+
+	nr_sep = 0;
+	while (*p) {
+		if (*p == ':')
+			nr_sep++;
+		if (nr_sep == 2)
+			break;
+		p++;
+	}
+
+	if (nr_sep == 2)
+		*p++ = '\0';
+	else
+		p = q;
+
+	strncpy(vdi, p, vdi_len);
+
+	p = strchr(vdi, ':');
+	if (p) {
+		*p++ = '\0';
+		*snapid = strtol(p, NULL, 10);
+	} else
+		*snapid = CURRENT_VDI_ID; /* search current vdi */
+
+	if (nr_sep == 2)
+		s->addr = q;
+	else {
+		free(q);
+		s->addr = NULL;
+	}
+
+	return 0;
+}
+
+static int find_vdi_name(struct bdrv_sd_state *s, char *filename, uint32_t snapid,
+			 uint32_t *vid, int for_snapshot)
+{
+	int ret, fd;
+	struct sd_vdi_req hdr;
+	struct sd_vdi_rsp *rsp = (struct sd_vdi_rsp *)&hdr;
+	unsigned int wlen, rlen = 0;
+	char buf[SD_MAX_VDI_LEN];
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0)
+		return -1;
+
+	memset(&hdr, 0, sizeof(hdr));
+	snprintf(buf, sizeof(buf), "%s", filename);
+	if (for_snapshot)
+		hdr.opcode = SD_OP_GET_VDI_INFO;
+	else
+		hdr.opcode = SD_OP_LOCK_VDI;
+	wlen = SD_MAX_VDI_LEN;
+	hdr.proto_ver = SD_PROTO_VER;
+	hdr.data_length = SD_MAX_VDI_LEN;
+	hdr.snapid = snapid;
+	hdr.flags = SD_FLAG_CMD_WRITE;
+
+	ret = do_req(fd, (struct sd_req *)&hdr, buf, &wlen, &rlen);
+	if (ret) {
+		ret = -1;
+		goto out;
+	}
+
+	if (rsp->result != SD_RES_SUCCESS) {
+		eprintf("%s, %s\n", sd_strerror(rsp->result), filename);
+		ret = -1;
+		goto out;
+	}
+	*vid = rsp->vdi_id;
+
+	ret = 0;
+out:
+	close(fd);
+	return ret;
+}
+
+static int add_aio_request(struct bdrv_sd_state *s, struct aio_req *aio_req,
+			   struct iovec *iov, int niov, int create,
+			   enum aiocb_state aiocb_type)
+{
+	int nr_copies = s->inode.nr_copies;
+	struct sd_obj_req hdr;
+	unsigned int wlen;
+	int ret, opt;
+	uint64_t oid = aio_req->oid;
+	unsigned int datalen = aio_req->data_len;
+	uint64_t offset = aio_req->offset;
+	uint8_t flags = aio_req->flags;
+	uint64_t old_oid = aio_req->base_oid;
+
+	if (!nr_copies)
+		eprintf("bug\n");
+
+	memset(&hdr, 0, sizeof(hdr));
+
+	if (aiocb_type == AIOCB_READ_UDATA) {
+		wlen = 0;
+		hdr.opcode = SD_OP_READ_OBJ;
+		hdr.flags = flags;
+	} else if (create) {
+		wlen = datalen;
+		hdr.opcode = SD_OP_CREATE_AND_WRITE_OBJ;
+		hdr.flags = SD_FLAG_CMD_WRITE | flags;
+	} else {
+		wlen = datalen;
+		hdr.opcode = SD_OP_WRITE_OBJ;
+		hdr.flags = SD_FLAG_CMD_WRITE | flags;
+	}
+
+	hdr.oid = oid;
+	hdr.cow_oid = old_oid;
+	hdr.copies = s->inode.nr_copies;
+
+	hdr.data_length = datalen;
+	hdr.offset = offset;
+
+	hdr.id = get_id_from_req(s, aio_req);
+
+	opt = 1;
+	setsockopt(s->fd, SOL_TCP, TCP_CORK, &opt, sizeof(opt));
+
+	ret = do_write(s->fd, &hdr, sizeof(hdr));
+	if (ret) {
+		eprintf("failed to send a req, %m\n");
+		return -EIO;
+	}
+
+	if (wlen) {
+		ret = do_writev(s->fd, iov, wlen, aio_req->iov_offset);
+		if (ret) {
+			eprintf("failed to send a data, %m\n");
+			return -EIO;
+		}
+	}
+        opt = 0;
+        setsockopt(s->fd, SOL_TCP, TCP_CORK, &opt, sizeof(opt));
+
+	return 0;
+}
+
+static int read_write_object(int fd, char *buf, uint64_t oid, int copies,
+			     unsigned int datalen, uint64_t offset,
+			     int write, int create)
+{
+	struct sd_obj_req hdr;
+	struct sd_obj_rsp *rsp = (struct sd_obj_rsp *)&hdr;
+	unsigned int wlen, rlen;
+	int ret;
+
+	memset(&hdr, 0, sizeof(hdr));
+
+	if (write) {
+		wlen = datalen;
+		rlen = 0;
+		hdr.flags = SD_FLAG_CMD_WRITE;
+		if (create)
+			hdr.opcode = SD_OP_CREATE_AND_WRITE_OBJ;
+		else
+			hdr.opcode = SD_OP_WRITE_OBJ;
+	} else {
+		wlen = 0;
+		rlen = datalen;
+		hdr.opcode = SD_OP_READ_OBJ;
+	}
+	hdr.oid = oid;
+	hdr.data_length = datalen;
+	hdr.offset = offset;
+	hdr.copies = copies;
+
+	ret = do_req(fd, (struct sd_req *)&hdr, buf, &wlen, &rlen);
+	if (ret) {
+		eprintf("failed to send a request to the sheep\n");
+		return -1;
+	}
+
+	switch (rsp->result) {
+	case SD_RES_SUCCESS:
+		return 0;
+	default:
+		eprintf("%s\n", sd_strerror(rsp->result));
+		return -1;
+	}
+}
+
+static int read_object(int fd, char *buf, uint64_t oid, int copies,
+		       unsigned int datalen, uint64_t offset)
+{
+	return read_write_object(fd, buf, oid, copies, datalen, offset, 0, 0);
+}
+
+static int write_object(int fd, char *buf, uint64_t oid, int copies,
+			unsigned int datalen, uint64_t offset, int create)
+{
+	return read_write_object(fd, buf, oid, copies, datalen, offset, 1, create);
+}
+
+/* TODO: error cleanups */
+static int sd_open(BlockDriverState *bs, const char *filename, int flags)
+{
+	int ret, i, fd;
+	uint32_t vid = 0;
+	struct bdrv_sd_state *s = bs->opaque;
+	char vdi[256];
+	uint32_t snapid;
+	int for_snapshot = 0;
+	char *buf;
+
+	strstart(filename, "sheepdog:", (const char **)&filename);
+
+	buf = qemu_malloc(SD_INODE_SIZE);
+	if (!buf) {
+		eprintf("Failed to allocate memory\n");
+		return -1;
+	}
+
+	for (i = 0; i < MAX_AIO_REQS; i++) {
+		s->aio_req_free[i] = &s->aio_req_list[i];
+		s->aio_req_list[i].aiocb = NULL;
+	}
+	s->nr_aio_req_free = MAX_AIO_REQS;
+
+	memset(vdi, 0, sizeof(vdi));
+	if (parse_vdiname(s, filename, vdi, sizeof(vdi), &snapid) < 0)
+		goto out;
+	s->fd = get_sheep_fd(s);
+	if (s->fd < 0)
+		return -1;
+
+	if (snapid != CURRENT_VDI_ID)
+		for_snapshot = 1;
+
+	ret = find_vdi_name(s, vdi, snapid, &vid, for_snapshot);
+	if (ret)
+		goto out;
+
+	if (snapid)
+		dprintf("%" PRIx32 " non current inode was open.\n", vid);
+	else
+		s->is_current = 1;
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		eprintf("failed to connect\n");
+		goto out;
+	}
+
+	ret = read_object(fd, buf, vid_to_vdi_oid(vid), 0, SD_INODE_SIZE, 0);
+
+	close(fd);
+
+	if (ret)
+		goto out;
+
+	memcpy(&s->inode, buf, sizeof(s->inode));
+	s->nr_dirty_data_oids = 0;
+
+	bs->total_sectors = s->inode.vdi_size >> 9;
+	strncpy(s->name, vdi, sizeof(s->name));
+	qemu_free(buf);
+
+	QLIST_INIT(&s->pending_head);
+	return 0;
+out:
+	qemu_free(buf);
+	return -1;
+}
+
+static int do_sd_create(const char *addr, char *filename, char *tag,
+			int64_t total_sectors, uint32_t base_vid,
+			uint32_t *vdi_id, int snapshot)
+{
+	struct sd_vdi_req hdr;
+	struct sd_vdi_rsp *rsp = (struct sd_vdi_rsp *)&hdr;
+	int fd, ret;
+	unsigned int wlen, rlen = 0;
+	char buf[SD_MAX_VDI_LEN];
+
+	fd = connect_to_sdog(addr);
+	if (fd < 0)
+		return -1;
+
+	strncpy(buf, filename, SD_MAX_VDI_LEN);
+
+	memset(&hdr, 0, sizeof(hdr));
+	hdr.opcode = SD_OP_NEW_VDI;
+	hdr.base_vdi_id = base_vid;
+
+	wlen = SD_MAX_VDI_LEN;
+
+	hdr.flags = SD_FLAG_CMD_WRITE;
+	hdr.snapid = snapshot;
+
+	hdr.data_length = wlen;
+	hdr.vdi_size = total_sectors * 512;
+
+	ret = do_req(fd, (struct sd_req *)&hdr, buf, &wlen, &rlen);
+
+	close(fd);
+
+	if (ret)
+		return -1;
+
+	if (rsp->result != SD_RES_SUCCESS) {
+		eprintf("%s, %s\n", sd_strerror(rsp->result), filename);
+		return -1;
+	}
+
+	if (vdi_id)
+		*vdi_id = rsp->vdi_id;
+
+	return 0;
+}
+
+static int sd_create(const char *filename, QEMUOptionParameter *options)
+{
+	int ret;
+	uint32_t vid = 0;
+	int64_t total_sectors = 0;
+	char *backing_file = NULL;
+
+	strstart(filename, "sheepdog:", (const char **)&filename);
+
+	while (options && options->name) {
+		if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
+			total_sectors = options->value.n / 512;
+		} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
+			backing_file = options->value.s;
+		}
+		options++;
+	}
+
+	if (backing_file) {
+		BlockDriverState bs;
+		char vdi[SD_MAX_VDI_LEN];
+		uint32_t snapid;
+
+		strstart(backing_file, "sheepdog:", (const char **)&backing_file);
+		memset(&bs, 0, sizeof(bs));
+
+		bs.opaque = qemu_malloc(sizeof(struct bdrv_sd_state));
+		if (!bs.opaque)
+			return -1;
+
+		ret = sd_open(&bs, backing_file, 0);
+		if (ret < 0)
+			return -1;
+
+		if (parse_vdiname(bs.opaque, backing_file, vdi, sizeof(vdi), &snapid) < 0)
+			return -1;
+
+		/* cannot clone from a current inode */
+		if (snapid == CURRENT_VDI_ID)
+			return -1;
+
+		ret = find_vdi_name(bs.opaque, vdi, snapid, &vid, 1);
+		if (ret)
+			return -1;
+	}
+
+	return do_sd_create(NULL, (char *)filename, NULL, total_sectors, vid,
+			    NULL, 0);
+}
+
+static void sd_close(BlockDriverState *bs)
+{
+	struct bdrv_sd_state *s = bs->opaque;
+	struct sd_vdi_req hdr;
+	struct sd_vdi_rsp *rsp = (struct sd_vdi_rsp *)&hdr;
+	unsigned int wlen, rlen = 0;
+	int fd, ret;
+
+	dprintf("%s\n", s->name);
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0)
+		return;
+
+	memset(&hdr, 0, sizeof(hdr));
+
+	hdr.opcode = SD_OP_RELEASE_VDI;
+	wlen = strlen(s->name) + 1;
+	hdr.data_length = wlen;
+	hdr.flags = SD_FLAG_CMD_WRITE;
+
+	ret = do_req(fd, (struct sd_req *)&hdr, s->name, &wlen, &rlen);
+
+	close(fd);
+
+	if (!ret && rsp->result != SD_RES_SUCCESS &&
+	    rsp->result != SD_RES_VDI_NOT_LOCKED)
+		eprintf("%s, %s\n", sd_strerror(rsp->result), s->name);
+
+	close(s->fd);
+	free(s->addr);
+}
+
+static void sd_write_done(struct sd_aiocb *acb)
+{
+	int ret, i;
+	struct bdrv_sd_state *s = acb->common.bs->opaque;
+	struct iovec iov;
+	struct aio_req *aio_req;
+	uint32_t offset, data_len, mn, mx;
+
+	if (s->nr_dirty_data_oids) {
+		mn = mx = s->dirty_data_oids[0];
+		for (i = 0; i < s->nr_dirty_data_oids; i++) {
+			if (mn > s->dirty_data_oids[i])
+				mn = s->dirty_data_oids[i];
+			if (mx < s->dirty_data_oids[i])
+				mx = s->dirty_data_oids[i];
+		}
+		offset = sizeof(s->inode) - sizeof(s->inode.data_vdi_id) +
+			mn * sizeof(s->inode.data_vdi_id[0]);
+		data_len = (mx - mn + 1) * sizeof(s->inode.data_vdi_id[0]);
+		s->nr_dirty_data_oids = 0;
+
+		iov.iov_base = &s->inode;
+		iov.iov_len = sizeof(s->inode);
+		aio_req = alloc_aio_req(s, acb, vid_to_vdi_oid(s->inode.vdi_id),
+					data_len, offset, 0, 0, offset);
+		if (!aio_req) {
+			eprintf("too many requests\n");
+			acb->ret = -EIO;
+			goto out;
+		}
+		ret = add_aio_request(s, aio_req, &iov, 1, 0, AIOCB_WRITE_UDATA);
+		if (ret) {
+			free_aio_req(s, aio_req);
+			acb->ret = -EIO;
+			goto out;
+		}
+
+		acb->aio_done_func = sd_finish_aiocb;
+		acb->aiocb_type = AIOCB_WRITE_UDATA;
+		return;
+	}
+out:
+	sd_finish_aiocb(acb);
+}
+
+static int sd_create_branch(struct bdrv_sd_state *s)
+{
+	int ret, fd;
+	uint32_t vid;
+	char *buf;
+
+	dprintf("%" PRIx32 " is not current.\n", s->inode.vdi_id);
+
+	buf = qemu_malloc(SD_INODE_SIZE);
+	if (!buf)
+		return -1;
+
+	ret = do_sd_create(s->addr, s->name, NULL, s->inode.vdi_size >> 9,
+			   s->inode.vdi_id, &vid, 1);
+	if (ret)
+		goto out;
+
+	dprintf("%" PRIx32 " is created.\n", vid);
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		eprintf("failed to connect\n");
+		goto out;
+	}
+
+	ret = read_object(fd, buf, vid_to_vdi_oid(vid), s->inode.nr_copies,
+			  SD_INODE_SIZE, 0);
+
+	close(fd);
+
+	if (ret < 0)
+		goto out;
+
+	memcpy(&s->inode, buf, sizeof(s->inode));
+
+	s->is_current = 1;
+	ret = 0;
+	dprintf("%" PRIx32 " was newly created.\n", s->inode.vdi_id);
+
+out:
+	qemu_free(buf);
+
+	return ret;
+}
+
+static void sd_readv_writev_bh_cb(void *p)
+{
+	struct sd_aiocb *acb = p;
+	int ret = 0;
+	unsigned long len, done = 0, total = acb->nb_sectors * 512;
+	unsigned long idx = acb->sector_num * 512 / SD_DATA_OBJ_SIZE;
+	uint64_t oid;
+	uint64_t offset = (acb->sector_num * 512) % SD_DATA_OBJ_SIZE;
+	struct bdrv_sd_state *s = acb->common.bs->opaque;
+	struct sd_inode *inode = &s->inode;
+	struct aio_req *aio_req;
+
+	qemu_bh_delete(acb->bh);
+	acb->bh = NULL;
+
+	if (acb->aiocb_type == AIOCB_WRITE_UDATA && !s->is_current) {
+		ret = sd_create_branch(s);
+		if (ret) {
+			acb->ret = -EIO;
+			goto out;
+		}
+	}
+
+	while (done != total) {
+		uint8_t flags = 0;
+		uint64_t old_oid = 0;
+		int create = 0;
+
+		oid = vid_to_data_oid(inode->data_vdi_id[idx], idx);
+
+		len = min_t(unsigned long, total - done, SD_DATA_OBJ_SIZE - offset);
+
+		if (!inode->data_vdi_id[idx]) {
+			if (acb->aiocb_type == AIOCB_READ_UDATA)
+				goto done;
+
+			create = 1;
+		} else if (acb->aiocb_type == AIOCB_WRITE_UDATA
+			   && !is_data_obj_writeable(inode, idx)) {
+			create = 1;
+			old_oid = oid;
+			flags = SD_FLAG_CMD_COW;
+		}
+
+		if (create) {
+			dprintf("update ino (%" PRIu32") %"
+				PRIu64 " %" PRIu64 " %" PRIu64 "\n",
+				inode->vdi_id, oid,
+				vid_to_data_oid(inode->data_vdi_id[idx], idx), idx);
+			oid = vid_to_data_oid(inode->vdi_id, idx);
+			dprintf("new oid %lx\n", oid);
+		}
+
+		aio_req = alloc_aio_req(s, acb, oid, len, offset, flags,
+					old_oid, done);
+		if (!aio_req) {
+			eprintf("too many requests\n");
+			acb->ret = -EIO;
+			goto out;
+		}
+
+		if (create) {
+			struct aio_req *areq;
+			QLIST_FOREACH(areq, &s->pending_head, pending_siblings) {
+				if (get_id_from_req(s, areq) == get_id_from_req(s, aio_req))
+					continue;
+				if (areq->oid == oid) {
+					aio_req->flags = 0;
+					aio_req->base_oid = 0;
+					goto done;
+				}
+			}
+		}
+
+		ret = add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov,
+				      create, acb->aiocb_type);
+		if (ret < 0) {
+			eprintf("add_aio_request is faled\n");
+			free_aio_req(s, aio_req);
+			acb->ret = -EIO;
+			goto out;
+		}
+	done:
+		offset = 0;
+		idx++;
+		done += len;
+	}
+out:
+	if (QLIST_EMPTY(&acb->aioreq_head))
+		sd_finish_aiocb(acb);
+}
+
+static BlockDriverAIOCB *sd_aio_writev(BlockDriverState *bs,
+				       int64_t sector_num,
+				       QEMUIOVector *qiov,
+				       int nb_sectors,
+				       BlockDriverCompletionFunc *cb,
+				       void *opaque)
+{
+	struct sd_aiocb *acb;
+
+	acb = sd_aio_setup(bs, qiov, sector_num, nb_sectors, cb, opaque);
+	acb->aio_done_func = sd_write_done;
+	acb->aiocb_type = AIOCB_WRITE_UDATA;
+
+	sd_schedule_bh(sd_readv_writev_bh_cb, acb);
+	return &acb->common;
+}
+
+static BlockDriverAIOCB *sd_aio_readv(BlockDriverState *bs,
+				      int64_t sector_num,
+				      QEMUIOVector *qiov,
+				      int nb_sectors,
+				      BlockDriverCompletionFunc *cb,
+				      void *opaque)
+{
+	struct sd_aiocb *acb;
+	int i;
+
+	acb = sd_aio_setup(bs, qiov, sector_num, nb_sectors, cb, opaque);
+	acb->aiocb_type = AIOCB_READ_UDATA;
+	acb->aio_done_func = sd_finish_aiocb;
+
+	/*
+	 * TODO: we can do better; we don't need to initialize
+	 * blindly.
+	 */
+	for (i = 0; i < qiov->niov; i++)
+		memset(qiov->iov[i].iov_base, 0, qiov->iov[i].iov_len);
+
+	sd_schedule_bh(sd_readv_writev_bh_cb, acb);
+	return &acb->common;
+}
+
+static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
+{
+	struct bdrv_sd_state *s = bs->opaque;
+	int ret, fd;
+	uint32_t new_vid;
+	struct sd_inode *inode;
+	unsigned int datalen;
+	uint64_t offset;
+
+	dprintf("sn_info: name %s id_str %s s: name %s vm_state_size %d "
+		"is_current %d\n", sn_info->name, sn_info->id_str,
+		s->name, sn_info->vm_state_size, s->is_current);
+
+	if (!s->is_current) {
+		eprintf("You can't create a snapshot of "
+			"a non current VDI, %s (%" PRIu32 ").\n",
+			s->name, s->inode.vdi_id);
+
+		return -1;
+	}
+
+	dprintf("%s %s\n", sn_info->name, sn_info->id_str);
+
+	s->inode.vm_state_size = sn_info->vm_state_size;
+	s->inode.vm_clock_nsec = sn_info->vm_clock_nsec;
+	offset = 0;
+	/* we don't need to read entire object */
+	datalen = SD_INODE_SIZE - sizeof(s->inode.data_vdi_id);
+
+	/* refresh inode. */
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		ret = -EIO;
+		goto cleanup;
+	}
+
+	ret = write_object(fd, (char *)&s->inode, vid_to_vdi_oid(s->inode.vdi_id),
+			   s->inode.nr_copies, datalen, offset, 0);
+	if (ret < 0) {
+		eprintf("failed to write snapshot's inode.\n");
+		ret = -EIO;
+		goto cleanup;
+	}
+
+	ret = do_sd_create(s->addr, s->name, NULL, s->inode.vdi_size >> 9,
+			   s->inode.vdi_id, &new_vid, 1);
+	if (ret < 0) {
+		eprintf("failed to create inode for snapshot. %m\n");
+		ret = -EIO;
+		goto cleanup;
+	}
+
+	inode = (struct sd_inode *)qemu_malloc(datalen);
+	if (!inode) {
+		eprintf("failed to allocate memory for inode. %m\n");
+		goto cleanup;
+	}
+
+	ret = read_object(fd, (char *)inode, vid_to_vdi_oid(new_vid),
+			  s->inode.nr_copies, datalen, offset);
+
+	close(fd);
+
+	if (ret < 0) {
+		eprintf("failed to read new inode info. %m\n");
+		ret = -EIO;
+		goto cleanup;
+	}
+
+	memcpy(&s->inode, inode, datalen);
+	dprintf("s->inode: name %s snap_id %x oid %x\n",
+		s->inode.name, s->inode.snap_id, s->inode.vdi_id);
+
+cleanup:
+	close(fd);
+	return ret;
+}
+
+static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
+{
+	struct bdrv_sd_state *s = bs->opaque;
+	struct bdrv_sd_state *old_s;
+	char vdi[SD_MAX_VDI_LEN];
+	char *buf = NULL;
+	uint32_t vid;
+	uint32_t snapid = 0;
+	int ret = -ENOENT, fd;
+
+	old_s = qemu_malloc(sizeof(struct bdrv_sd_state));
+	if (!old_s) {
+		eprintf("failed to allocate memory for old state. %m\n");
+		goto out;
+	}
+
+	memcpy(old_s, s, sizeof(struct bdrv_sd_state));
+
+	snapid = strtol(snapshot_id, NULL, 10);
+	if (!snapid) {
+		eprintf("Invalid snapshot_id\n");
+		goto out;
+	}
+
+	buf = qemu_malloc(SD_INODE_SIZE);
+	if (!buf) {
+		eprintf("Failed to allocate memory\n");
+		goto out;
+	}
+	strncpy(vdi, s->name, sizeof(vdi));
+	ret = find_vdi_name(s, vdi, snapid, &vid, 1);
+	if (ret) {
+		eprintf("Failed to find_vdi_name\n");
+		ret = -ENOENT;
+		goto out;
+	}
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		eprintf("failed to connect\n");
+		goto out;
+	}
+
+	ret = read_object(fd, buf, vid_to_vdi_oid(vid), s->inode.nr_copies,
+			  SD_INODE_SIZE, 0);
+
+	close(fd);
+
+	if (ret) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	memcpy(&s->inode, buf, sizeof(s->inode));
+
+	if (!s->inode.vm_state_size) {
+		eprintf("Invalid snapshot\n");
+		ret = -ENOENT;
+		goto out;
+	}
+
+	s->is_current = 0;
+
+	qemu_free(buf);
+	qemu_free(old_s);
+
+	return 0;
+out:
+	/* recover bdrv_sd_state */
+	memcpy(s, old_s, sizeof(struct bdrv_sd_state));
+	qemu_free(buf);
+	qemu_free(old_s);
+
+	eprintf("failed to open. recover old bdrv_sd_state.\n");
+
+	return ret;
+}
+
+static int sd_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
+{
+	/* FIXME: Delete specified snapshot id.  */
+	return 0;
+}
+
+#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
+#define BITS_PER_BYTE		8
+#define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
+#define DECLARE_BITMAP(name,bits) \
+	unsigned long name[BITS_TO_LONGS(bits)]
+
+#define BITS_PER_LONG (BITS_PER_BYTE * sizeof(long))
+
+static inline int test_bit(unsigned int nr, const unsigned long *addr)
+{
+	return ((1UL << (nr % BITS_PER_LONG)) &
+		(((unsigned long *)addr)[nr / BITS_PER_LONG])) != 0;
+}
+
+static int sd_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
+{
+	struct bdrv_sd_state *s = bs->opaque;
+	struct sd_req req;
+	int i, fd, nr = 1024, ret, max = BITS_TO_LONGS(SD_NR_VDIS) * sizeof(long);
+	QEMUSnapshotInfo *sn_tab = NULL;
+	unsigned wlen, rlen;
+	int found = 0;
+	static struct sd_inode inode;
+	unsigned long *vdi_inuse;
+	unsigned int start_nr;
+
+	vdi_inuse = qemu_malloc(max);
+	if (!vdi_inuse)
+		return 0;
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0)
+		goto out;
+
+	rlen = max;
+	wlen = 0;
+
+	memset(&req, 0, sizeof(req));
+
+	req.opcode = SD_OP_READ_VDIS;
+	req.data_length = max;
+
+	ret = do_req(fd, (struct sd_req *)&req, vdi_inuse, &wlen, &rlen);
+
+	close(fd);
+	if (ret)
+		goto out;
+
+	sn_tab = qemu_mallocz(nr * sizeof(*sn_tab));
+	if (!sn_tab)
+		goto out;
+
+	start_nr = fnv_64a_buf(s->name, strlen(s->name), FNV1A_64_INIT) & (SD_NR_VDIS - 1);
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		eprintf("failed to connect\n");
+		goto out;
+	}
+
+	/* TODO: round up */
+	for (i = start_nr; i < SD_NR_VDIS && found < nr; i++) {
+		if (!test_bit(i, vdi_inuse))
+			break;
+
+		/* we don't need to read entire object */
+		ret = read_object(fd, (char *)&inode, vid_to_vdi_oid(i),
+				  0, SD_INODE_SIZE - sizeof(inode.data_vdi_id), 0);
+
+		if (ret)
+			continue;
+
+		if (!strcmp(inode.name, s->name) && inode.snap_ctime) {
+			sn_tab[found].date_sec = inode.snap_ctime >> 32;
+			sn_tab[found].date_nsec = inode.snap_ctime & 0xffffffff;
+			sn_tab[found].vm_state_size = inode.vm_state_size;
+			sn_tab[found].vm_clock_nsec = inode.vm_clock_nsec;
+
+			snprintf(sn_tab[found].id_str, sizeof(sn_tab[found].id_str), "%u",
+				 inode.snap_id);
+			found++;
+		}
+	}
+
+	close(fd);
+out:
+	*psn_tab = sn_tab;
+
+	qemu_free(vdi_inuse);
+
+	return found;
+}
+
+static int do_load_save_vmstate(struct bdrv_sd_state *s, uint8_t *data,
+				int64_t pos, int size, int load)
+{
+	int fd, create;
+	int ret = 0;
+	unsigned int data_len;
+	uint64_t vmstate_oid;
+	uint32_t vdi_index;
+	uint64_t offset;
+
+	fd = connect_to_sdog(s->addr);
+	if (fd < 0) {
+		ret = -EIO;
+		goto cleanup;
+	}
+
+	while (size) {
+		vdi_index = pos / SD_DATA_OBJ_SIZE;
+		offset = pos % SD_DATA_OBJ_SIZE;
+
+		data_len = min_t(unsigned int, size, SD_DATA_OBJ_SIZE);
+
+		vmstate_oid = vid_to_vmstate_oid(s->inode.vdi_id, vdi_index);
+
+		create = (offset == 0);
+		if (load)
+			ret = read_object(fd, (char *)data, vmstate_oid,
+					  s->inode.nr_copies, data_len, offset);
+		else
+			ret = write_object(fd, (char *)data, vmstate_oid,
+					   s->inode.nr_copies, data_len, offset, create);
+
+		if (ret < 0) {
+			eprintf("failed to save vmstate %m\n");
+			ret = -EIO;
+			goto cleanup;
+		}
+
+		pos += data_len;
+		size -= data_len;
+		ret += data_len;
+	}
+cleanup:
+	close(fd);
+	return ret;
+}
+
+static int sd_save_vmstate(BlockDriverState *bs, const uint8_t *data,
+			   int64_t pos, int size)
+{
+	struct bdrv_sd_state *s = bs->opaque;
+
+	return do_load_save_vmstate(s, (uint8_t *)data, pos, size, 0);
+}
+
+static int sd_load_vmstate(BlockDriverState *bs, uint8_t *data,
+			   int64_t pos, int size)
+{
+	struct bdrv_sd_state *s = bs->opaque;
+
+	return do_load_save_vmstate(s, data, pos, size, 1);
+}
+
+
+static QEMUOptionParameter sd_create_options[] = {
+	{
+		.name = BLOCK_OPT_SIZE,
+		.type = OPT_SIZE,
+		.help = "Virtual disk size"
+	},
+	{
+		.name = BLOCK_OPT_BACKING_FILE,
+		.type = OPT_STRING,
+		.help = "File name of a base image"
+	},
+	{ NULL }
+};
+
+BlockDriver bdrv_sheepdog = {
+	.format_name = "sheepdog",
+	.protocol_name = "sheepdog",
+	.instance_size = sizeof(struct bdrv_sd_state),
+	.bdrv_file_open = sd_open,
+	.bdrv_close = sd_close,
+	.bdrv_create = sd_create,
+
+	.bdrv_aio_readv = sd_aio_readv,
+	.bdrv_aio_writev = sd_aio_writev,
+
+	.bdrv_snapshot_create = sd_snapshot_create,
+	.bdrv_snapshot_goto = sd_snapshot_goto,
+	.bdrv_snapshot_delete = sd_snapshot_delete,
+	.bdrv_snapshot_list = sd_snapshot_list,
+
+	.bdrv_save_vmstate = sd_save_vmstate,
+	.bdrv_load_vmstate = sd_load_vmstate,
+
+	.create_options = sd_create_options,
+};
+
+static void bdrv_sheepdog_init(void)
+{
+	bdrv_register(&bdrv_sheepdog);
+}
+block_init(bdrv_sheepdog_init);